Can with peelably bonded closure

ABSTRACT

A metal can for holding a carbonated or otherwise pressurized beverage or the like, having a rigid metal lid formed with an eccentrically disposed, upwardly projecting annular flange defining an aperture of average diameter between about 0.625 inch and about 1 inch, and a flexible metal foil closure extending over the aperture and peelably bonded by a heat seal to the sloping outer surface of the flange.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of copending U.S.patent application Ser. No. 09/905,310, filed Jul. 13, 2001, which is acontinuation-in-part of U.S. patent application Ser. No. 09/603,004,filed Jun. 26, 2000 (now abandoned), which is a continuation-in-part ofU.S. patent application Ser. No. 09/247,999, filed Feb. 10, 1999 (nowabandoned), the entire disclosures of all of the aforesaid applicationsbeing incorporated herein by this reference.

BACKGROUND OF THE INVENTION

[0002] This invention relates to cans, and more particularly to metalcans having an apertured lid with a heat-sealed, peelable closure forthe aperture. In an important specific aspect it is directed toheat-sealed-closure type cans for holding carbonated beverages or likecontents that exert a positive internal pressure on the closure, andalso to lids for such cans, carbonated beverage-containing packagesincluding such cans, and methods of producing such cans containingcarbonated beverages.

[0003] Heat sealable containers are widely used for a variety of highquality food products. Non-retorted products packaged with heat sealablefoil lidding include many types of jams, preserves, yogurt and dairyproducts, peanuts and snack foods. A wide variety of retortable fish andmeat products (including many varieties of pet food) are also packagedusing heat sealed foil lidding. In some instances, the entire lid of acan or like container may be removably bonded by heat sealing to aflange formed at an open upper end of the container body, so as toenable the lid to be completely removed, for access to the contents ofthe container. Other containers, exemplified by cans of tomato or likequiescent fruit juices, have a lid permanently secured to the containerbody and formed with an aperture (for pouring out the contents) coveredby a heat sealed closure or, more commonly, by a closure bonded with apressure sensitive adhesive. Such a closure is commonly a thin, flexibleelement, e.g. an aluminum foil-polymer laminate, peripherally bonded byheat sealing to a flange defining the aperture, and has a tab thatenables the closure to be peeled manually from the flange; the flangemay be a flat portion of the can lid surrounding the aperture andcoplanar with the aperture edge.

[0004] For easy opening, typical peel forces (at 90° to the flange) fora heat sealed closure are in a range between about 2 lbs. (≈9 Newtons)and 4 lbs. (18 Newtons) and preferably about 2½ lbs. (≈11.3 Newtons).

[0005] Some containers with heat sealed closures are subjected to aretorting process after filling to sterilize the food or beverage. Theretort process involves pressure differentials (from inside to outside)of up to 30 psi (≈2 bar), although for many applications, a counterpressure system is used to prevent the lid or closure from bursting offthe container. This is necessary because of the reduction in bondstrength which generally occurs at the elevated retort temperatures.Moreover, in the case of containers with a lid or closure heat sealed toa flange which is coplanar with the container aperture, internalpressure will cause the lid or closure to bulge over the aperture and,in turn, this bulging exerts a peel force on the heat seal.

[0006] Carbonated soft drinks require a container capable ofwithstanding internal pressures of 90 psi or higher. Such pressures, oreven substantially lesser positive internal pressures, would exert on aconventional heat sealable closure a peeling force more than sufficientto cause burst failure. Increasing the strength of the heat seal bondsufficiently to withstand such forces would make manual peeling of theclosure difficult or virtually impossible for many consumers.Consequently, heat sealable closures have not had wide commercial usewith canned carbonated beverages. In present-day commercially availablecarbonated soft drink cans, having a so-called drawn-and-ironed aluminumalloy can body and an aluminum alloy can lid peripherally secured to theopen upper end of the body, the can end is commonly formed with a scoredarea and provided with a riveted tab system which, when lifted, createsa lever action and exerts a downward force that generates a fracturealong a scored line thereby creating an aperture. The region of the lidthat lies within the scored area is simultaneously bent down into thetop of the container.

[0007] A conventional can end or lid provided with a riveted tab andscored area must be fabricated from sheet which has sufficient strengthand formability to meet the requirements. In particular, the gauge,alloy and temper must be chosen to meet the demands of the rivet-formingoperation, to enable the scoring (which typically has a depth equal toabout half the thickness of the lid) to withstand internal pressureswhich may exceed 90 psi (≈6 bar), and to impart sufficient strength tothe rivet area of the lid so that the score line can be ruptured bymanual application of a leveraged force using the tab. The aluminumalloy designated AA5182, rolled to about 0.0086″ (≈218μ) gauge currentlymeets these requirements in the most cost effective way. However,compared to some other sheet alloy products (for example, AA3104 canbody sheet), it is quite costly. This is due in part to thecomparatively high magnesium content (≈4.5% by weight) and also due tothe more costly rolling practices which are necessary for this alloy.Moreover, during recycling and remelting operations, magnesium ispreferentially oxidized, and therefore lost in the dross. This meansthat metal from recycled used beverage containers (UBCs) is not suitablefor can end sheet production unless costly additions of magnesium aremade to compensate for this magnesium loss.

[0008] In addition, the full can end must have sufficient strength andrigidity when attached to the can so that it will not buckle, reverse ordeflect excessively under the stresses applied by the internal pressurefrom the contained beverage; the larger the area of a can lid, thegreater is the strength necessary to prevent deflection and buckling orreversal. In recent years, there has been some reduction in commercialcan end (lid) diameter, with concomitant reduction in lid gauge andarea, affording savings in amount of metal used per lid. However, aconventional can lid must have a diameter large enough to accommodatethe tab and the centrally positioned rivet as well as a scored area ofsufficient size to provide the desirably large aperture currentlypreferred for pouring or drinking; this consideration has constrainedthe extent to which the diameter of conventional lids can be reduced.Also, even with the limited lid diameter reduction heretofore achieved,a conventional lid is ordinarily formed with a peripheral countersink toaid in minimizing deflection and reduce the likelihood of buckling orreversal of the lid, although the presence of the countersink(unavoidably near the location of drinking or pouring) isdisadvantageous from a hygienic standpoint in that, especially duringstorage, it may collect dirt and foreign matter.

[0009] Another disadvantage of the riveted tab - scored area system isthat the score line is vulnerable to corrosive attack. Scoring of thecan end cuts through the protective layer of lacquer and exposes acrevice of unprotected metal. Any spillage or contamination of thisscore line by a beverage or other liquid may initiate localizedcorrosive attack.

[0010] Alternative structures have heretofore been proposed or producedwith the objective of enabling use of heat sealable closures withcontainers for carbonated beverages or other substances that createelevated internal pressure. For instance, it has been proposed toprovide a spherically domed (rather than planar) lid having an aperturecovered by a similarly spherically curved closure member bonded thereto,or to provide a container in which the entire lid is heat-sealed to anangled (rather than planar) flange around the container periphery. In afurther alternative, a can lid has been provided with plural small holes(rather than a single aperture) covered by a single foil laminate sealwith a pull tab. These alternatives, however, have various limitationsor drawbacks.

[0011] U.S. Pat. No. 3,889,844 describes a can closure in which a canend is shaped to impart a frustoconical area around a pour hole sealedwith an adhesive tape tab so that the forces acting on the tape (exertedby can contents under pressure, such as carbonated beverages) tend toplace the adhesive in shear instead of in peel. The size of the pourhole described in this patent provides a pour rate which is low ascompared to present-day conventional carbonated beverage cans withscored can ends, and the attainment of long shelf life at pressures ashigh as 90 psi is not shown.

SUMMARY OF THE INVENTION

[0012] The present invention, in a first aspect, broadly contemplatesthe provision of a can comprising a metal can body having an open upperend; a substantially rigid metal can lid secured at its periphery to andclosing the can body end, the lid having an upper surface; an annularflange formed in a portion of the lid and projecting upwardly from thelid upper surface, the flange having an upwardly sloping outer surfaceand an annular inner edge lying substantially in a plane and defining anaperture with an average diameter between about 0.625 inch and about 1inch; and a flexible closure member of a material comprising a metalfoil, extending entirely over the aperture and peelably bonded by a heatseal to the flange outer surface entirely around the aperture.

[0013] In currently preferred embodiments of the invention, the lid hasa substantially flat upper surface. It is also strongly currentlypreferred that the aperture be circular, because in noncircularapertures there are locations around the perimeter where the tendency ofthe closure member to peel (burst) is enhanced. The “average diameter”in the case of a circular aperture is, of course, simply the diameter ofthe aperture.

[0014] It will be understood that directions such as “upper” or“upwardly” are used herein with reference to a can standing upright withthe lid at the top.

[0015] Further in accordance with the invention, in currently preferredembodiments thereof, the flange outer surface is oriented at an angle ofslope between about 12.5° and about 40° to the plane of the annularinner edge (aperture edge) of the flange; a currently especiallypreferred range for the angle is between about 20° and about 35°. Theterm “angle of slope” refers to the acute angle formed between the planeof the aperture edge and the line representing the flange outer surfaceas seen in a vertical plane intersecting the aperture edge at a point atwhich the line tangent to the aperture edge in the plane of the apertureedge is perpendicular to the vertical plane. The sloping outer surfaceof the annular flange may be straight-sided, i.e. frustoconical, orcurved; if the surface is curved, the angle of slope is the angle of theline tangent thereto, in the aforesaid vertical plane, immediatelyadjacent the aperture edge.

[0016] When the can is filled with a carbonated beverage, the closuremember is subjected to a differential pressure (hereinafter sometimesdesignated Δ_(P)), i.e. a positive difference between the pressurewithin the can and ambient pressure outside the can, in somecircumstances as high as 90 psi or even more. This differential pressureexerts, on the closure member and heat seal, a force having a tear/shearcomponent (i.e., tending to tear the closure member and shear the heatseal, such component being hereinafter referred to as the tear/shearforce and being sometimes designated γ), and in some cases also a peelcomponent.

[0017] In currently preferred embodiments of the invention, the closuremember material is deformable, and the average diameter of the aperture,the angle of slope of the flange, and the deformability of the materialare mutually selected such that the closure member, when subjected todifferential pressures up to at least about 90 psi (preferably up to atleast about 100 psi) in the can, bulges upwardly with an arc ofcurvature such that a line tangent to the arc at the inner edge of theflange lies at an angle (to the plane of the flange inner edge) notsubstantially greater than the angle of slope of the flange outersurface, thereby to eliminate any peel component of the force exerted bythe differential pressure on the closure member and heat seal.

[0018] Also, in some currently preferred embodiments, the closure memberand heat seal have a tear/shear force resistance of at least about 75lb./in., and the average diameter of the aperture and the angle of slopeof the flange are mutually selected such that when the closure member issubjected to differential pressure of up to at least about 90 psi(preferably up to at least about 100 psi) within the can, the tear/shearforce exerted on the closure member and heat seal does not exceed theaforesaid tear/shear force resistance.

[0019] As a further particular feature of the invention, in currentlypreferred embodiments, the annular inner edge of the flange is formedwith a reverse bead curl, which may be substantially tangent to theupwardly sloping outer surface of the flange.

[0020] Conveniently and advantageously, in at least many instances, themetal foil of the closure member is aluminum alloy foil, e.g. having athickness between about 0.002 inch (≈50μ) and about 0.004 inch (≈100μ).Also advantageously, the heat seal may be formed as an annulussurrounding the aperture and having a width between about 0.079 inch andabout 0.118 inch (about 2 to 3 mm). This width of heat seal is found tobe sufficient to withstand tear/shear forces encountered in use, and atthe same time it facilitates manual peeling of the closure member toopen the aperture. To enable such peeling without difficulty, the 90°peel strength of the heat seal is between about 8 and about 20 N,preferably between about 10 and about 16 N. The closure may be providedwith a tab portion having a manually graspable free end.

[0021] In contrast to the riveted tab structure of conventionalcarbonated beverage cans, a heat-sealable closure member may becomecompletely separated from the can upon opening, and may then beseparately discarded, creating environmental problems. To avoid thisconsequence, and further in accordance with the invention, the closuremay be provided with an extension overlying the lid in opposed relationto the aforementioned tab portion, and the heat seal may include both anannulus surrounding the aperture as described above and a further sealportion bonding the extension to the lid such that the peel forcerequired to separate the extension from the lid is greater than thatrequired to separate the closure member from the lid at the annulus, theaperture being easily opened by peeling back the closure member from theflange while the closure member remains secured to the lid by thefurther seal portion. This promotes retention of the closure member onthe lid, as desired for environmental reasons. Moreover, the peeled butretained metal foil closure member can be folded over the aperture toprovide a measure of coverage and protection for the contents of a canwhich has been only partially emptied.

[0022] Additionally, a body of fragrance-providing material may bedisposed between the closure member and the lid and surrounded by theheat seal such that when the closure member is subjected to a peel forceeffective to open the aperture, the body of fragrance-providing materialbecomes exposed. The fragrance thereby released, in proximate relationto the nostrils of a person drinking from the can, enhances theeffective flavor sensed by the drinker.

[0023] The can body may be a drawn and ironed metal can body for holdinga carbonated beverage. The lid may be formed with a peripheral rimengaging the open upper end of the can body and projecting upwardlyabove the upper surface of the lid, the body being formed with anoutwardly concave lower end, and the rim and body lower end beingmutually shaped and dimensioned to permit stable vertical stacking ofthe can with other identically shaped and dimensioned cans. In such astructure, although the flexible closure member (bulging because of theinternal pressure) is domed so as to rise to a height above the annularflange, the height of the rim, the concavity of the body lower end, andthe height to which the closure rises above the annular flange are suchthat there is sufficient clearance between the lid upper surface of thecan and the concave bottom of another identical can stacked above it toaccommodate the domed closure.

[0024] Metal foil as used for the closure (e.g. as a lacquered foil oras part of a foil-polymer laminate) has the advantage of affordingexcellent gas barrier properties, so that the shelf life and quality ofthe product are comparable to that which is obtained with a normal can,or a glass bottle, and superior to most other beverage container systems(including PET bottles and other polymer containers). Aluminum foil, forinstance, is an effectively perfect barrier for oxygen (important forbeer to prevent development of off-flavors owing to oxidation) and forcarbon dioxide (important where carbonation levels need to bemaintained). It is also an effective barrier to prevent migration andloss of fragrance and flavor components.

[0025] The aperture defined by the flange preferably extends over aminor fraction of the area of the open end of the can body. Especiallyfor holding contents such as carbonated beverages, in cans wherein theopen end of the can body has a center of symmetry (e.g. being circular),the annular flange and the aperture are disposed eccentrically of thecan body open end so as to be relatively close to the periphery of thelid, for ease of pouring or drinking. That is to say, the flange isdisposed in a portion of the lid eccentric to the geometric axis of thecan, i.e., close to a side of the can.

[0026] Although the shape of the aperture can take different forms,noncircular apertures are nonpreferred, and, in particular, angularapertures or aperture shapes with very small radii of curvature are notsuitable for the present invention. If, instead of a circular aperture,an elliptical or irregularly shaped aperture is provided, e.g. having anaspect ratio between about 1.1 and 1.5, the flange (even ifstraight-sided) is not strictly frustoconical; it will be understoodthat the term “frustoconical” is used broadly herein to define anupwardly convergently sloping straight-sided flange continuouslysurrounding an aperture, whether the aperture is circular or not.

[0027] In further aspects, the invention embraces a can lid member asdescribed above, mountable on a metal can body having an open upper endso as to be peripherally secured to and to close the can body end; thecombination of this lid member with a flexible closure member extendingentirely over the aperture and peelably bonded to the flange outersurface around the aperture; a carbonated or otherwise pressurizedbeverage package comprising a can as described above in combination witha body of a pressurized beverage contained within the can; and a methodof producing a can containing a pressurized beverage, comprising fillinga drawn and ironed metal can body, having an open upper end, with apressurized beverage, and closing the open upper end of the can body byperipherally securing thereto a metal can lid member as described abovehaving a flexible closure member extending entirely over the aperturedefined by its annular flange and peelably bonded to the flange outersurface around the aperture.

[0028] In the can of the invention, the provision of the upwardlyprojecting annular flange defining the can aperture, and the securing ofthe flexible closure member by peelable bonding to the upwardly slopingouter surface of this flange, enable the use of a peelably bondedclosure member on an otherwise conventional carbonated beverage can,despite the high differential pressure (positive internal pressure)acting on the closure through the aperture and the resultant outwardbulging or doming of the flexible closure member. This is because theangle of slope of the flange can be made steep enough so that a linetangent to the arc of curvature of the domed closure member at the inneredge of the flange lies at an angle (to the plane of the flange inneredge) which is not substantially greater than, and is preferably lessthan, the angle of slope of the flange outer surface. In such case, theinternal pressure acting on the closure member does not exert anysignificant component of peeling force that would tend to separate theclosure member from the flange by peeling. Instead, the forces acting onthe peelably bonded flange area owing to tension in the closure memberare predominantly shear in character. Heat seal bonds, for instance, arestrong under shear loading, especially at ambient temperature; theinability of conventional heat sealed closures to withstand internalpressure in carbonated beverage cans has been caused by the substantialpeeling forces exerted on such closures when the closures bulge, underthe elevated pressure within a can of carbonated beverage, at asubstantial angle to a planar horizontal flange surrounding an aperture.

[0029] For a given internal pressure condition, aperture dimension, andclosure member, the minimization or elimination of peeling force exertedon a closure bond by elevated pressure within the can is dependent onthe angle of slope of the flange. Stated generally, the greater theangle of slope, the easier it is to provide a bonded closure that willnot burst from internal pressure yet can be easily manually peeled by aconsumer, having regard to the extent of doming of practicable flexiblefoil closure members under the pressures within a carbonated beveragecan. With the flat lid surface and upwardly projecting frustoconicalflange of the present invention, any desired angle of slope can readilybe provided, in contrast to the range of angles permitted by othergeometries such as a uniformly spherically domed lid having an aperturetherein. Moreover, the arrangement of flange, aperture, and domedclosure of the invention, occupying only a portion of the area of thecan end, enables the height of the closure to be restricted to an extentcompatible with convenient vertical stacking of cans.

[0030] The use of a can end or lid having an aperture with a peelableheat-sealed closure, in accordance with the present invention asdescribed above, affords additional advantages in that the strengthand/or the size of the lid may be reduced (without decreasing thedesired size of the aperture for pouring or drinking), as compared to aconventional can lid having a riveted tab and scored area. This isbecause the strength and size requirements imposed on the lid by theriveted tab and scoring are eliminated. In addition, the formingoperations for the flange and aperture of the present invention are lessdemanding than for a riveted tab, the most critical being the formationof the reverse bead curl, in embodiments of the invention including thatfeature.

[0031] Reduction in strength requirements enables use of a lessexpensive alloy for the lid than the AA5182 currently used, and/or areduction in lid gauge, thereby affording savings in metal cost. Forexample, in particular embodiments of the invention, the lid may befabricated of an alloy similar in composition to AA5182, but with areduced concentration of magnesium. Alternatively, AA3104 or 3004alloys, which are the alloys most commonly used for the can body, couldbe used. In each case, the gauge of the sheet would be selected toprovide the desired property combination. For the case of AA3104 alloy,the can end and can body would be the same alloy and this isadvantageous in several respects. For example, the recycling of usedbeverage cans (UBCs) benefits from the reduced magnesium oxide drossformation. Furthermore, there are benefits to be gained during metalprocessing. For example, since only one alloy is used for the can endand can body, the casting and rolling scheduling can be greatlysimplified and rolling mill schedules can be optimized for a singlealloy, allowing improvements in mill productivity. Similarly, it shouldbe possible to reduce metal inventories. Alternatively, the lid may bemade of other metals, such as steel, that are unsuitable for a rivetedtab and scored area opening system.

[0032] Reduction in size requirements, a result of the elimination ofthe need to accommodate the riveted tab at a central location on the lidwhile also affording adequate area for a pouring/drinking opening ofpreferred large size, further reduces strength requirements. Whereas alid diameter of about 2⅛ inches represents a currently practicable lowerlimit for a can with a riveted tab and a scored area providing adesirably large opening, with the present invention the lid diameter canadvantageously be reduced to less than 2 inches, indeed substantiallyless, yet without reducing the size of the pouring/drinking aperture.Since a reduced lid size will have a reduced tendency to buckle whenpressurized, the gauge of metal used can be reduced by at least about 5%below the current value of 0.0086 inch (≈218μ) used with 2⅛ inchdiameter AA5182 alloy lids. Alternatively, the design of the lid can bemodified to eliminate the countersink recess which is conventionallyformed in the peripheral area of can lids to prevent stiffening andthereby to prevent excessive deflection and buckling. In yet a furtheralternative, the reduced tendency of a smaller diameter lid to bucklecan be exploited by using a lower strength alloy than AA5182, with theadvantages in cost and recycling mentioned above.

[0033] The reduction in lid size attainable with the invention requiresa reduction in diameter, or formation of a neck, in the upper portion ofthe can body on which the lid is mounted, so as to conform to the smalllid diameter without detracting from the fluid capacity of the can. Tothis end, the upper part of the sidewall of a conventional drawn andironed can body may be subjected to one or more neck-forming operationsthat reduce the upper body diameter to conform to the lid.Alternatively, the drawing and ironing operation may be modified so asto form the necked portion from the bottom portion of the can body(which is of higher gauge than the sidewall), forming an open end forthe neck, and closing the other end of the can body (which, in thisembodiment, is the lower end) by seaming a plain can end thereto beforefilling. The reduced diameter lid with the flanged aperture andheat-sealed closure is then seamed onto the open neck after the can isfilled.

[0034] More generally, in the cans and lids of the invention thecountersink may be reduced or eliminated even if the lid is ofconventional diameter, owing to the stiffening effect of the annularflange, in combination with a suitable choice of alloy and gauge;additional stiffening features such as ribs, coined regions and/orraised or depressed panel areas may also be formed in the lid when thecountersink is reduced or omitted.

[0035] Further features and advantages of the invention will be apparentfrom the detailed disclosure hereinbelow set forth, together with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1 is a perspective view of a can embodying the presentinvention in a particular form;

[0037]FIG. 2A is an enlarged and somewhat simplified fragmentaryelevational sectional view of a portion of the lid member of the can ofFIG. 1, including the aperture-defining flange and closure member;

[0038]FIG. 2B is a highly simplified and schematic representation of thesame view as FIG. 2A;

[0039]FIG. 3 is a view similar to FIG. 2A of a flexible closure memberbonded to a conventional planar flange defining an aperture;

[0040]FIG. 4 is a fragmentary view similar to FIG. 3 of a portion of theflange and closure member of the embodiment of the invention shown inFIGS. 2A and 2B;

[0041]FIG. 5 is a simplified and somewhat schematic top plan view of thecan of FIG. 1;

[0042]FIG. 6 is an exploded diagrammatic elevational sectional view ofthe can lid and closure member of FIG. 5;

[0043]FIG. 7 is a plan view of the closure member of FIG. 5;

[0044]FIG. 8 is a side elevational view, partly broken away, of two canshaving the structure shown in FIG. 1, illustrating the ability of thecans to be stacked vertically;

[0045]FIG. 9 is a view similar to FIG. 2B illustrating a condition ofexcessive bulging of the closure member;

[0046]FIG. 10 is a graph representing the relationship between sealingtemperature and peel strength in Example 2 described below;

[0047]FIG. 11 is a graph representing the relationship between heat sealtemperature and burst pressure in the same example;

[0048]FIG. 12 is an enlarged fragmentary sectional elevational view of aportion of a lid member embodying the present invention;

[0049]FIG. 13 is a schematic fragmentary sectional elevational view of alid member embodying the invention;

[0050]FIG. 14 is a graph showing bulge height of an exemplary closuremember as a function of pressure within the can (i.e., differentialpressure Δ_(P));

[0051]FIG. 15 is a schematic plan view of a can lid embodying theinvention and having a “stay-on” closure member;

[0052]FIG. 16 is a graph showing 90° peel force as a function ofdisplacement of the closure member of FIG. 15;

[0053]FIGS. 17A and 17B are highly schematic fragmentary elevationalsectional views in illustration of a further embodiment of the inventionincluding a fragrance reservoir;

[0054]FIG. 18 is a sectional elevational view of one form of can lidembodying the invention and including a fragrance reservoir;

[0055]FIGS. 19 and 20 are views similar to FIG. 15 of two can lidsembodying the invention and including both a stay-on closure member anda fragrance reservoir;

[0056]FIG. 21 is a sectional view of another form of can lid embodyingthe invention, in which the conventional countersink is omitted;

[0057]FIG. 22 is an elevational view of a further embodiment of the canof the invention, having a reduced-diameter body neck and lid;

[0058]FIG. 23 is an enlarged fragmentary perspective view of the upperportion of the can of FIG. 22, showing the lid with the heat-sealedclosure member in place;

[0059]FIG. 24 is a view similar to FIG. 23 with the closure memberremoved;

[0060]FIG. 25 is an elevational view of another embodiment of the can ofthe invention;

[0061]FIG. 26 (prior art) is an exploded and highly schematic sectionalview in illustration of a system for producing a conventional drawn andironed can body;

[0062]FIG. 27 is a fragmentary view, similar to FIG. 26, of one form ofmodification of the system of FIG. 26 for producing the body of the canof FIG. 25;

[0063]FIG. 28 is an elevational view of the can body as formed by thesystem of FIG. 27;

[0064]FIG. 29 is a view similar to FIG. 27 of an alternativemodification of the system of FIG. 26 for producing the body of the canof FIG. 25;

[0065]FIGS. 30A, 30B and 30C are simplified fragmentary elevationalsectional views of can lids in accordance with the inventionrespectively having a conventional countersink, a countersink of reduceddimensions, and no countersink;

[0066]FIGS. 31A, 31B, 31C, 31D and 31E are simplified and greatlyenlarged fragmentary perspective views of types of stiffening featuresthat may be formed in a can lid;

[0067]FIGS. 32A and 32B are, respectively, a plan view and anelevational sectional view of a can lid, embodying the invention andomitting a countersink, with added stiffening features;

[0068]FIGS. 33A and 33B are, respectively, a plan view and anelevational sectional view of another can lid, embodying the inventionand omitting a countersink, with added stiffening features; and

[0069]FIGS. 34A and 34B are, respectively, a plan view and anelevational sectional view of yet another can lid, embodying theinvention and omitting a countersink, with added stiffening features.

DETAILED DESCRIPTION

[0070] The container of the invention will be described, with referenceto the drawings, as embodied in a metal can 10 for holding a carbonatedbeverage such as soda or beer. The can 10 includes a one-piece can body11 constituting the bottom 12 and continuous, upright, axiallyelongated, generally cylindrical side wall 14 of the can, and a lid 16which, after the can has been filled with the beverage, is peripherallysecured to the open top end of the can body to provide a complete,liquid-tight container.

[0071] In this embodiment, the body 11 may be an entirely conventionaldrawn-and-ironed aluminum alloy can body, identical in structure, alloycomposition, method of fabrication, configuration, gauge, dimensions andsurface coatings to can bodies currently commercially used forcarbonated and other beverages (alternatively, for example, the body maybe a steel can body, such as are in common use in Europe). Inparticular, and in common with known can bodies, the bottom 12 of thebody 11 is externally concave and the open top end of the body has acircular edge 18 lying in a plane perpendicular to the verticalgeometric axis of the side wall 14. The terms “aluminum” and “aluminumalloy” are used interchangeably herein to designate aluminum metal andaluminum-based alloys.

[0072] Except as hereinafter described, the lid 16 may also be agenerally conventional aluminum alloy lid member of the type currentlycommercially used for beverage cans having drawn and ironed one-piececan bodies such as the body 11. Thus, the alloy of which it isconstituted, the steps and procedures employed in its fabrication (withthe exceptions noted below), and its general overall configuration,dimensions, gauge and surface coatings as well as the manner in which itis secured to the top edge 18 of the can body 11, may all be the same asin the case of present day can lids well-known in the art.

[0073] It should be noted, however, that since the can lid of thepresent invention is not subjected to the rivet-forming and scoringoperations that must be performed on currently conventional can lids,since the strength and rigidity necessary for the conventional rivet andtab area to withstand the lever action are not required, and since gaugeand strength requirements related to the presence of a score line do notapply, the invention permits the use of nonconventional can lid alloys,materials and/or lid gauges. For example, coated steel can lids, whichare normally too difficult to open by the conventional scoringmechanisms, could be used in the practice of the invention. The currentgauge used for AA 5182 alloy lids could be reduced and/or the alloycomposition could be modified by reducing the proportion of Mg, therebylowering costs. Similarly, AA 5182 alloy could be replaced as the alloyof the lid with a lower cost, lower strength alloy such as AA 3104 alloyor AA3004 alloy, commonly used for can bodies (but not, heretofore, forcan lids). Used at an appropriate gauge, AA 3104 alloy or AA 3004 alloymay have sufficient strength for the lid structure of the presentinvention; it could offer the advantages of lower cost as compared tothe AA 5182 alloy currently used for can lids and would also affordbenefits for recycling, in that the can lid and body would be made ofthe same alloy.

[0074] In particular, the lid 16 in this illustrated embodiment issubstantially rigid, and has a substantially flat upper surface 20 witha circular periphery, around which is formed a raised annular rim 22projecting upwardly above the plane of the flat upper surface 20. Whenthe lid is mounted on the open upper end of a beverage-filled can body,in known manner, the rim 22 engages the upper edge 18 of the can body;the circular flat surface 20 lies substantially in a horizontal plane,perpendicular to the vertical geometric axis of the cylindrical sidewall 14, and is centered with respect to the latter axis.

[0075] The lower end 14 a of the side wall 14 of the can 10 is shaped(tapered) to interfit with the rim 22 of the lid of another identicalcan 10 a, when the can 10 is stacked vertically on top of the can 10 aas shown in FIG. 8. A multiplicity of the cans may thus be stablyvertically stacked, one on another, as is true of present-dayconventional cans of the same general type. The elevation of the lid rim22 above the flat upper surface 20 of the lid, together with theconcavity of the can bottom 14, cooperatively define a central gap orspace between the lid of one can and the bottom of the next can aboveit, in such a stacked arrangement.

[0076] Also in common with present-day conventional lid members usedwith one-piece drawn-and-ironed aluminum alloy beverage can bodies, thelid 16, when secured to the beverage-filled can body, provides therewitha complete sealed enclosure holding the beverage. The lid is thussubjected to elevated internal pressure within the can (i.e., pressurehigher than ambient atmospheric pressure) if the beverage is carbonated.However, the formed aluminum alloy lid is substantially rigid, so thatit undergoes at most only a small deflection of its upper surface as aresult of this pressure condition, and the upper surface 20 remainssubstantially flat notwithstanding the internal pressure acting on thelid.

[0077] The lid 16 is arranged to provide an aperture through which thebeverage contained in the can may be poured or removed by drinkingdirectly from the can, either with a straw inserted through the apertureor by juxtaposition of the consumer's mouth to the aperture. Heretofore,in cans for holding carbonated beverages or other such contents atelevated pressure, the aperture-providing feature has conventionallyincluded a scored portion of the metal of the lid member and a rivetedpull tab system for parting the lid metal along the score line to openthe aperture.

[0078] The present invention, in contrast, provides a pre-formed openaperture 24 in the lid, and a peelable, flexible closure member 28covering the aperture. In order to achieve adequate burst resistancewithout requiring excessive force to peel the closure member, a shallowupwardly projecting annular flange 30 is formed in the lid within thearea of the flat upper surface 20, to surround and define the aperture24 and to provide a seat for the closure member. For purposes ofillustration, the flange 30 and its counterparts in other embodiments ofthe invention hereinbelow described are shown as frustoconical (i.e.,having straight-sided upwardly sloping outer surfaces), but it is to beunderstood that the upwardly sloping outer surface of such a flange, incans and lids of the present invention, may alternatively be a curvedsloping surface.

[0079] More particularly, the flange 30 projects upwardly from the uppersurface 20 of the lid, and has an upwardly sloping outer flange surface32 and an annular inner edge 34 defining the aperture 24, which isillustrated as being of circular configuration but is not limited to acircular shape. The inner edge 34, as shown in FIGS. 2A and 2B, ispreferably formed as a bead 36 with a reverse curl, which is tangent toa horizontal plane represented by line P (FIGS. 2A and 2B) and to theline of slope of the outer flange surface 32 so that, once the closuremember 28 is heat-sealed to the flange surface, the cut metal (typicallyan aluminum alloy) at edge 34 cannot come into contact with thecontained beverage. This is advantageous because the cut metal at theedge (unlike the major surfaces of the lid) has no protective coating,and would be attacked by acidic or salt-containing beverages if it wereexposed thereto. The reverse curl of bead 36 also prevents a drinker'slips from touching and being injured by the cut metal at edge 34, andavoids any possibility of damage to the closure member by contact withthe cut metal. However, the invention may also be embodied in a canwherein the aperture has a standard (not reverse) bead curl, which alsoaffords such benefits as safety for the consumer, it being noted thatwhere the cut edge of the metal is not kept from contact with thecontained liquid by a reverse curl, it may be protected by applicationto the cut edge of a lacquer.

[0080] The flexible closure member 28 is constituted of a sheet materialcomprising metal foil, e.g. aluminum foil; in the described embodimentof the invention, the closure member is fabricated of a suitablylacquered aluminum foil sheet or an aluminum foil-polymer laminatesheet. Stated more broadly, materials that may be used for the closuremember include, without limitation, lacquer coated foil (where thelacquer is a suitable heat seal formulation); extrusion coated foil(where the polymer is applied by a standard or other extrusion coatingprocess); the aforementioned foil-polymer laminate, wherein the foil islaminated to a polymer film using an adhesive tie layer; andfoil-paper-lacquer combinations such as have heretofore been used forsome low-cost packaging applications.

[0081] The closure member extends entirely over the aperture 24 and issecured to the flange outer surface 32 by a heat seal extending at leastthroughout the area of an annulus entirely surrounding the aperture.Since the reverse curl bead 36 does not project beyond the slope of theflange outer surface, the closure member smoothly overlies this bead aswell as the flange outer surface, affording good sealing contact betweenthe closure member and the flange.

[0082] The closure member, in the described embodiment of the invention,is bonded by heat sealing to the flange 30, covering and closing theaperture 24, before the lid member 16 is secured to a can body 11 filledwith a carbonated beverage. Once the lid has been mounted on the body tocomplete the enclosure of the beverage, elevated pressure generated bythe beverage acts on the inner surface portion of closure member 28which is exposed through the aperture to the interior of the can,causing the flexible closure member to bulge outwardly. Further inaccordance with the invention, however, the angle θ (FIG. 2A) of slopeof the flange outer surface relative to the plane of the annular edge 34(i.e., plane P) is selected to be such that a line tangent to the arc ofcurvature of the bulged closure member at the inner edge of the flangelies at an angle to plane P not substantially greater than the angle θof slope of the flange outer surface. As indicated in FIG. 2B, since theupper surface 20 of the lid member 16 is flat and horizontal (and thusparallel to plane P), θ may alternatively be defined as the angle ofslope of the flange outer surface to the flat lid surface 20.

[0083] Preferably the angle θ is between about 12.5° and about 40° tothe plane P; a more preferred lower limit for θ is about 15°, and a morepreferred upper limit is about 35°, or even in some instances about 30°.In currently particularly preferred embodiments, the angle θ of slope isbetween about 20° and about 35° to the plane P.

[0084] After initial forming of the flange there is some spring-back ofthe metal so that tooling with a 35° forming angle will result (afterspring-back) in a flange angle of about 30°. Furthermore, when the canis pressurized, the can end bows and the effective flange angle isfurther reduced, by an amount which depends on the internal pressure butis typically a few degrees. For the burst resistance calculationsdiscussed below, it is the actual angle of the flange when the can ispressurized that is relevant (i.e., after spring-back and the bowing ofthe can end are taken into account) and not the angle of the formingtool.

[0085] In FIGS. 2A and 2B, A is the diameter of the aperture 24 in planeP, R is the radius of curvature of the bulged or domed closure member28, and h is the maximum vertical height of the domed closure memberabove the aperture plane P. In these figures, the foil closure is showndomed to the point at which the flange is tangential to the arc of thedomed foil closure member 28, i.e., at which the line of slope of theflange surface 32 as seen in a vertical plane is tangent to the arc ofcurvature of the closure 28 (as seen in the same vertical plane) at theedge of aperture 24.

[0086] For the closure configuration illustrated in FIGS. 2A and 2B, theforces acting on the heat sealed flange area due to the tension in thefoil, are predominantly shear in character, with no significant peelforce component. In this case, the burst resistance will depend on theshear strength of the heat seal joint or the bulge strength of the foilor foil laminate itself. This ensures that the burst resistance of thelid is enhanced significantly compared to that of a standard heat sealedcontainer.

[0087] Heat seal bonds are strong under shear loading, especially atambient temperature, and an annular heat seal about 2 mm-3 mm wide issufficient to resist the anticipated shear forces which result from theinternal pressure. If the foil is domed to a lesser extent than shown inFIGS. 2A and 2B, relative to the flange slope angle θ, the foil laminatewill tend to hold down the heat seal bond with a correspondingadditional enhancement of the burst resistance. If, however, the foilwere domed to a greater extent than is shown in FIGS. 2A and 2B,relative to the flange slope angle, a peel force component would ariseat the inner edge of the aperture, with an increased likelihood of burstfailure.

[0088] The frustoconical aperture-defining flange enables provision of aflange slope angle θ sufficient to accommodate the extent of doming orbulging of the closure member to be used therewith, under the elevatedinternal pressures for which the can is designed, and thereby enablesthe burst resistance to be enhanced significantly, for a closure with apeel force which is acceptable to the consumer. The peel force isdependent both on the inherent peel properties of the selected heat seallacquer system, and on geometric effects associated with the complexbending and distortion which the closure foil undergoes during peeling.

[0089] As will therefore be clear, the flange slope angle and the formof the foil closure strongly influence the burst resistance. In additionto the flange slope angle and extent of doming of the closure, not onlythe resistance of the heat seal bond to shear forces but also thestrength of the foil of the closure member are selected to withstand theforces acting thereon. If the flange slope angle, in accordance with theinvention, is such as to substantially avoid any substantial peel forcecomponent of forces acting on the heat sealed area owing to tension inthe foil from the internal pressure acting on the closure member, and ifthe heat seal bond and the shear resistance of the bond are adequate,burst failure could occur by failure of the foil itself. The shear forcerequired to break the heat seal bond can be adjusted either byincreasing the width of the heat sealed region, or by selectinglaminates or coating formulations which achieve a higher shear strength.Both of these expedients, however, would increase the peel forcerequired to open the container.

[0090] The effect of heat sealing the closure member 28 to a slopingflange surface rather than a horizontal flange surface, will be apparentfrom a comparison of FIGS. 3 and 4. FIG. 3 represents an aperture 40 ina conventional lid member 41 wherein the flange 42 around the apertureis simply a flat horizontal portion of the lid upper surface, coplanarwith the aperture edge 43. A flexible closure member 44 covering theaperture 40 and bonded by heat sealing to the coplanar flange 42 willbulge, in the same manner as the closure member 28 in FIG. 2A, if thelid member 41 is mounted on a can body filled with a carbonated beverageor other pressure-generating contents. Assuming that equal elevatedpressures exist within the cans of FIGS. 2A and 3, that the diameters ofapertures 24 and 40 are equal, and that the same flexible sheet materialis used for the closure members 28 and 44, the extent of bulging of theclosure members (defined by h and R) should be essentially identical inboth cans. In the case of the planar flange of FIG. 3, the consequenttension force F_(T) acting on the heat-seal-bonded portion of theclosure member 44 at the edge of the aperture 40 will have a substantialpeeling force component F_(P) acting at 90° to the plane of the flangesurface. In the case of the sloping flange of the invention, however, asshown in FIG. 4, owing to the above-described relation of angle θ to theangle of the tangent to the arc of curvature of the domed closure member28 at the aperture edge 34 (in which, in FIG. 4, the reverse curl isomitted for simplicity of illustration), the same tension force F_(T)(which acts in the direction of the aforementioned tangent at the edgeof the aperture) has no significant peeling force component F_(P) actingin direction D at 90° to the plane of the (sloping) flange surface 32.

[0091] Under the pressures that may obtain within a can of carbonatedbeverage, the peeling force component F_(p) acting on a flange that iscoplanar with the aperture edge can be sufficient to cause the closuremember to progressively separate from the flange by peeling until itbursts open, at least if the strength of the heat seal bond is withinconventional limits as desired for ease of peeling by a user. Thesloping of the flange prevents this from happening, and therebyincreases the burst resistance of the heat-sealed closure membersufficiently to enable its safe use on a carbonated beverage can withouthaving to increase the heat seal bond strength to a point which wouldmake the closure member difficult to remove by a user.

[0092] It will be understood that the extent of bulging of the closuremember under the influence of pressure within the can, and thus theangle of the tangent (relative to plane P) to the bulged or domedclosure member at the aperture edge, is dependent on the pressure withinthe can and the elastic deformability of the closure member. Desirably,the slope angle θ of the flange surface 32 should be chosen to besufficiently large so as to be compatible with the bulgingcharacteristic of the chosen closure member material. The provision ofthe flange, which serves as a seat for the heat sealing of the closuremember, as a frustoconical projection from a (preferably substantiallyflat) upper surface of a substantially rigid lid, facilitates thisprovision of a relatively large slope angle. At the same time, by makingthe aperture area a minor fraction of the total area of the can openend, the height h of the domed closure may readily be kept sufficientlysmall to be accommodated between the lid of one can and the concavebottom of another when the cans are stacked vertically as shown in FIG.8.

[0093] Further, it will be understood that the benefits of the inventionmay be realized even if the flexible closure member bulges slightlybeyond the ideal limit of tangency to the slope of the flange. In such acase, the peel component of force will start to grow, but may still beinsufficient to cause failure of the bond.

[0094] FIGS. 5-7 illustrate further the configuration and arrangement ofthe flange, aperture and closure member at the top of the can in theembodiment of FIG. 1. With a circular can lid member 16 having adiameter of 48 mm, mountable on a can body having a correspondinglydimensioned circular open upper end, a circular aperture 24 having adiameter of 20 mm is defined by a frustoconical annular flange 30 havinga maximum diameter (in the plane of lid surface 20) of 30 mm. As bestseen in FIG. 7, the foil-polymer laminate closure member 28 has acircular central portion 32 mm in diameter (large enough to completelyoverlie the sloping outer surface of the flange), with a shortprojection 28 a on one side for overlying part of the flat upper surfaceof the lid and an integral tab portion 28 b on the opposite side which,outwardly of the flange 30, is not heat sealed but is free to be bentand pulled. The exploded diagrammatic elevational view of FIG. 6indicates the relative positions of the can lid 16 and the closuremember 28, as well as the folding of the tab. The closure member issubjected to a preliminary forming step to impart a frustoconical shape(also indicated in FIG. 6) to its circular central portion for properseating on and sealing to the flange 30.

[0095] The aperture 24 is shown in FIG. 5 as being disposedeccentrically of the geometric center (center of symmetry) of the canlid 16, i.e., relatively close to the edge of the lid, so that a usercan easily bring the aperture to his or her mouth for drinking thecontained beverage directly from the can. However, depending on use andcontents, different positions for the aperture may be employed. Also, ifdesired, aperture configurations other than the circular shape shown maybe provided.

[0096] The manufacture of the can of the invention, includingparticularly the lid and closure, may (as stated) be in many respectsgenerally conventional. However, certain modifications of conventionalpractice and equipment, now to be described, are employed to achieve thenovel flange shape and the heat sealing of the closure member thereto.

[0097] Illustratively, but without in any way limiting the inventionthereto, the foil closure stock may be a suitable aluminum foil (e.g.made of alloy AA3104 or of a conventional foil alloy such as AA3003,8011, 8111, 1100, 1200) with a foil gauge of 0.002″-0.004″ (≈50μ to100μ) which is either lacquered on one side with a suitable heatsealable lacquer, or laminated on one side with a suitable heat sealablepolymer film (e.g., polyethylene, polypropylene, etc.), 0.001″-0.002″(≈25μ to 50μ ) thick. The other (outwardly exposed) side should have asuitable protective lacquer coating. It may be desirable to print ontothe foil using rotogravure, flexographic or another known printingmethod. It may also be desirable to emboss the laminate, or just thepull tab portion thereof, to provide an attractive surface texture whichenhances the appearance of the closure and assists in opening by makingthe closure easier to grip.

[0098] In order to seal to the aperture, the closure members 28 withtheir described integral pull tabs are formed and stamped out from thefoil laminate stock using a suitable press (standard presses can be usedwith tooling specifically designed for these closure members). In theembodiment where the frustoconical flange is preformed, the foil closuremembers are preshaped (by a drawing process) so that they will fit overthe raised aperture of the lid.

[0099] A heat sealing machine with suitable tooling is used to heat sealthe closures to the can lid. In the case where the frustoconical flangeis preformed, the heat seal tooling is designed to conform to the flangeshape. That is to say, the tooling is angled to match the flange (andthe formed closure member). The exact heat sealing conditions aredependent on the polymer and heat seal coating formulation used. Thetemperature of the bottom heat sealing tool should be selected so thatthe coating on the inside of the lid member should not be significantlysoftened or melted during the heat sealing operation. For the commonlyused can end coatings and for heat seal dwell times of about 0.3 sec. orless, the temperature should be less than about 220° C. and preferablyabout 200° C. or below. The upper tool temperature is set to ensure thatthe heat seal bond is achieved in an acceptably short time. Typicalcommercial heat sealing machines have dwell times of 0.3 sec. The dwelltime, pressure and temperatures may be optimized for the particular heatseal application. Heat sealing the closure to the lid involves use of acustomized heat sealing line (such as those built by Hans Rychiger AG,Steffisburg, Switzerland), with appropriately constructed heat sealtooling provided to bond the closure to the angled aperture.

[0100] The forming of the can lid member 16 itself with thefrustoconical flange 30 and aperture 24 as described is relativelystraightforward, using modified can end forming tooling, with provisionfor forming the reverse curl bead 36. The can lids of the invention donot require the formation of a rivet or tab.

[0101] The lids, complete with heat sealed closures, are substantiallycompatible with existing can filling lines and will be a directreplacement for the currently commercially used lids for cans forcarbonated beverages and the like. Modifications may be made in the lidhandling equipment to minimize or eliminate the possibility of damagingthe raised aperture and closure.

[0102] Alternatively, in the currently preferred method of fabrication,the can lid may initially be provided with the aperture 28 and reversecurl bead 36 around the edge thereof, and the closure member 28 may beheat sealed to the upper surface of the lid in covering relation to theaperture, before the upwardly sloping frustoconical configuration isimparted to the flange portion of the lid immediately surrounding theaperture. Forming of the frustoconical flange 30 then proceeds, withconcomitant deformation of the already heat sealed foil closure member,followed by mounting of the lid on a can body already filled withcarbonated beverage.

[0103] As initially applied to the can lid, the portion of the closuremember 28 extending across the aperture may be substantially planar asindicated at 28 c in FIG. 12, which shows a frustoconical flange 30having an angle of slope θ of 23°. When the lid is mounted on a can bodyfilled with a carbonated beverage, so as to completely enclose thebeverage, the resultant pressure within the can creates a positivedifferential pressure Δ_(P) causing the deformable closure member tobulge upwardly. FIG. 13 illustrates the location of the heat sealannulus 46 on the sloping outer surface of the frustoconical flange 30.

[0104] A particular feature of the present invention is the dimension ofthe aperture 24. There is a consumer preference for cans with goodpouring characteristics (good pour rate with a smooth, streamlinedflow). Cans with large opening ends (LOEs) have been introduced inrecent years and have been successful, especially for beverages withlower carbonation levels (e.g. lemonade and iced tea), although in thecase of highly carbonated beverages, problems with score line failureand burst resistance have been encountered. A conventional shape ofapertures for beverage cans is approximately oval with an aspect ratiobetween about 1.1 and about 1.5. A standard aperture is 0.7 inch indiameter and an LOE is 1 inch×0.7 inch; thus, the current aperture sizefor a carbonated beverage container, expressed as average diameter, isfrom about 0.7 inch to about 0.875 inch.

[0105] Some can designs have also provided a separate vent hole in thelid to improve pouring and drinking characteristics, but the inclusionof the vent hole adds to manufacturing cost and may complicate theopening process for the consumer.

[0106] The aperture size and shape are important in determining pouringand drinking characteristics. In general, larger aperture sizes givebetter flow rates with a more even flow. The relation between apertureand flow rates is illustrated by the following test data obtained inexperimental pouring tests with the can tilted from the upright positionthrough an angle of 120°, so that the can walls make an angle of 30° tothe horizontal, and oriented so that the aperture is at its lowest pointon the can end: TABLE 1 Aperture Pour Rate (g./sec.) Standard canaperture 56 LOE 70 0.5625″ (14.3 mm), flat flange 18 0.625″ (15.9 mm),flat flange 31 0.750″ (19.0 mm), flat flange 50 0.875″ (22.2 mm), flatflange 75 0.5625″ (14.3 mm), angled flange 24 0.625″ (15.9 mm), angledflange 35 0.750″ (19.0 mm), angled flange 56 0.875″ (22.2 mm), angledflange 93

[0107] In the above table, “angled flange” means an upwardly slopingfrustoconical flange as provided in the present invention; “flat flange”means that the portion of the lid surrounding the aperture issubstantially coplanar with the aperture edge, as in conventional canlids.

[0108] As will be apparent from Table 1, for equivalent hole sizes, thepour rate for “angled flange” apertures is higher by about 10 to 15% ata 30° tilt than that for “flat flange” apertures. The 0.750″ angledflange aperture has a pouring rate at 30° tilt approximately the same asthat of the current standard can aperture. The 0.5625″ aperture (withboth flat and angled flanges) has a significantly lower pour rate thanthat of the current standard can aperture. The 0.875″ angled flangeaperture provides a higher pour rate than the LOE design (which, likethe standard can, has a flat flange). For the aperture range ofinterest, the pour rate is approximately proportional to aperture area.

[0109] As hereinafter further explained, the tear/shear forces acting onthe closure member and seal tend to increase with aperture size, so thatthe maximum aperture diameter is limited by the need to provide a canwith adequately high burst pressure or burst resistance (i.e., thepressure at which the closure member and seal rupture or fail) .Therefore, the range of average aperture diameter in accordance with thepresent invention is between about 0.625 inch and about 1 inch, toafford satisfactory pour rates (without any separate vent hole) and atthe same time to achieve high burst resistance without sacrifice ofother characteristics such as peelability.

[0110] Another important characteristic, for attainment of adequatelyhigh burst resistance, is the tear/shear force imposed on the heat sealand closure member by a given differential pressure. The tear/shearforce γ (lb./in.) is determined by the differential pressure Δ_(P)(psi), aperture diameter A (inches) and angle of slope θ of thefrustoconical flange 30, in accordance with the relation $\begin{matrix}{\gamma = \frac{A \cdot \Delta_{p}}{4\sin \quad \theta}} & (1)\end{matrix}$

[0111] In particular instances, depending (for example) on the degree ofcarbonation of the contained beverage and the consequent magnitude ofdifferential pressure that the can, closure and seal must be designed towithstand, the design value of tear/shear force resistance for a can inaccordance with the invention (i.e., the value that the closure memberand heat seal must be able to withstand) may range from less than (orabout) 25 lb./in. to about (or even somewhat more than) 75 lb./in., atear/shear resistance of about 75 lb./in. being currently preferred inmany cases. Typical filling line pressures for carbonated beverages arebetween about 50 and about 60 psi, though for some beverages (sportsdrinks, lemonade, etc.), lower carbonation levels are used. However, inorder to take account of extreme conditions (temperature, agitation,etc.) a minimum test burst pressure requirement of 90 psi is currentlyspecified for many applications, and a burst resistance of 100 psi wouldbe even more desirable.

[0112] Table 2 sets forth values calculated using relation (1) above fortear/shear force γ (lb./in.) for various aperture diameters A and flangeslope angles θ at a differential pressure Δ_(P) of 100psi. TABLE 2 γ(lb./in.) θ° A = 0.500″ 0.625″ 0.750″ 0.875″ 1.000″ 1.125″ 1.250″ 2.5286.6 358.2 429.9 501.5 573.1 644.8 716.4 5 143.4 179.3 215.1 251.0286.8 322.7 358.6 7.5 95.8 119.7 143.6 167.6 191.5 215.5 239.4 10 72.090.0 108.0 126.0 144.0 162.0 180.0 12.5 57.8 72.2 86.6 101.1 115.5 129.9144.4 15 48.3 60.4 72.4 84.5 96.6 108.7 120.7 17.5 41.6 52.0 62.4 72.783.1 93.5 103.9 20 36.5 45.7 54.8 64.0 73.1 82.2 91.4 22.5 32.7 40.849.0 57.2 65.3 73.5 81.7 25 29.6 37.0 44.4 51.8 59.2 66.5 73.9

[0113] These are the minimum strength requirements (lb./in.) for theclosure member and heat seal to withstand a pressure differential Δ_(P)of 100 psi without rupture or failure (bursting), for each specifiedcombination of aperture diameter A and slope angle θ. As is apparent,for a given differential pressure, the tear/shear force strengthrequirement decreases with increasing flange angle and increases withincreasing aperture diameter.

[0114] By way of illustration, an aperture diameter of 0.875 inch and aflange angle of about 22.5° would require a closure foil with a breakingstrength in excess of 57.2 lb./in. and an equivalent minimum heat sealshear strength, for burst resistance of 100 psi.

[0115] Typical aluminum lidding foils of 0.003 inch thickness canwithstand a tear force in excess of 75 lb./in. Practicable heat sealscapable of withstanding a shear force of 75 lb./in. can also readily beprovided, in configurations suitable for the heat seal 46. Therefore,combinations of A and θ in Table 2 for which the calculated value of γis 75 lb./in. or less enable satisfactory and practicable attainment ofa burst resistance of 100 psi in the can of the present invention.

[0116] As already stated, to avoid a peel component in the force exertedon the closure member and heat seal by the differential pressure Δ_(P),the bulge height h of the closure member above the plane P of theaperture 24 should not exceed a value h_(max) at which the slope of theflange 30 is tangent to the arc of the bulging closure at the edge ofthe aperture. This upper limiting value h_(max) (in inches) is, again,determined by the angle of slope θ of the flange and the aperturediameter A (in inches) of the aperture 24; in the case of a circularaperture, such limiting value can be calculated using the relation$\begin{matrix}{h_{\max} = {\frac{A}{2}\left( {\frac{1}{\sin \quad \theta} - \frac{1}{\tan \quad \theta}} \right)}} & (2)\end{matrix}$

[0117] It will be seen that the maximum permitted bulge height, toachieve the described freedom from any peel component, increases withaperture diameter and also increases with flange angle.

[0118] The actual bulge height in a closure member 28 produced by agiven differential pressure Δ_(P) is dependent on the properties of theclosure foil related to deformation, i.e., the deformability of thefoil, as well as on the aperture diameter. FIG. 14 illustrates therelationship of bulge height h (here given in mm) to pressure Δ_(P) fora ⅞ inch aperture diameter and an exemplary aluminum foil 100μ (0.004inch) thick. The Figure has been corrected for the small initialdisplacement of the foil relative to the flange (i.e., the foil was notperfectly flat after the forming and springback). The measurements weremade with a lid clamped into place in the “buckle-tester.” The positionof the center of the foil covered aperture was measured carefully (usinga precision laser measurement device) and the pressure was graduallyincreased. Measurements were taken at intervals of 10 psi up to 80 psiand the displacement at each pressure was computed and plotted in FIG.14.

[0119] Examples of the maximum permitted bulge height (inches) asdefined above, calculated for a circular aperture using relation (2),for various combinations of A (in inches) and θ, are set forth in Table3: TABLE 3 h_(max) (in.) A (in.) θ° = 17.5 20 22.5 25 27.5 30 0.6250.048 0.055 0.062 0.069 0.076 0.084 0.750 0.058 0.066 0.075 0.083 0.0920.100 0.875 0.067 0.077 0.087 0.097 0.107 0.117 1.000 0.077 0.088 0.0990.111 0.122 0.134

[0120] For an aperture diameter of 0.875 inch with a flange slope angleof 22.50, the maximum bulge height should be 0.087 inch to avoid peelforce components.

[0121] If the bulge height exceeds the critical value, FIG. 14 can beused to determine the angle of the tangent to the arc of the bulgingclosure foil at the edge of the aperture. If the stress within the foilcan be determined, the peel component of the stress can be estimated.Provided that this component is less than the measured peel stress forthe closure material, failure by peeling will not occur. However, it ispreferred that the lid parameters be chosen to ensure that the bulgeheight does not exceed the above-defined limiting value at least fordifferential pressures up to 90 psi, more preferably for differentialpressures up to 100 psi.

[0122] Metal foils have comparatively good creep resistance over therange of temperatures that may be experienced in service, and thereforeafford an important advantage over polymeric closure member materialswith respect to creep susceptibility and consequent short shelf life.Since creep is dependent on applied stress, increasing the thickness ofthe closure material can reduce or eliminate creep. For aluminum foilclosure members, a thickness between about 0.003 and about 0.004 inch(about 75-100μ) is sufficient to virtually eliminate creep.

[0123] The performance of the bond between the closure membrane and thelid flange is dependent on the properties of the adhesive layer and onthe design of the joint. The flange angle is designed to ensure that theforces between the closure membrane and the flange are predominantlyshear in character under the fully pressurized conditions of use.However, the shear stress in the joint can be affected by the width ofthe heat seal; i.e., increasing the width of the bond spreads the loadand thereby reduces the stress intensity.

[0124] It is desirable for the width of the heat seal to be less thanabout 0.118 inch (3 mm) and preferably about 0.079 inch (2 mm). If thewidth is increased above about 0.118 inch (3 mm), the peel forcerequired to open the container will be increased. Furthermore, anincreased heat seal (and flange) width would mean that the drinkingaperture has to be located further from the container edge, detractingfrom the convenience of the consumer by making the container lesscomfortable and more inconvenient to drink from.

[0125] Experimentally, it is found that a 0.079 inch (2 mm) wide heatseal annulus for the foil closure performs well in the can of theinvention (see Example 4 below). Fully pressurized cans (60-70 psi) havebeen stored at ambient temperature (≈20° C.) for several months, with nodetectable sign of creep in either the foil or in the adhesive bondjoint.

[0126] In containers for beverages and the like with manually peelableclosures, the peel force required to open the container shouldpreferably fall within the range between about 1.8 lb. and 4.5 lb. (8Nand 20N), and still more preferably within the range between about 2.25lb. and 3.6 lb. (10N and 16N) as measured by a 90° peel test. The peelforce required is dependent on the peel strength of the bond and on theeffective width of the seal during the peeling procedure. In the case ofan angled flange, there will also be a geometrical factor, which willaffect the final peel force required. The strength and gauge of the foilwill also contribute to peel strength since the peel action requires thefoil to be bent and deformed.

[0127] In the case of heat seal bonding, the peel strength is influencedby the particular lacquer formulations on the two mating surfaces, andon the heat sealing conditions which are used. For example, in onepreferred embodiment, the outer can end panel surface has a thin vinyllacquer coating (Valspar Unicoat, up to about 2μ thick) and the aluminumfoil closure material has a vinyl based heat seal lacquer (AlcanRorschach TH388, between about 5 and 8μ thick).

[0128] For this combination of coatings, the peel strength falls withinan acceptable range for peelability. At the same time, provided theclosure foil has sufficient strength, the heat seal bond can meet therequirements for shear strength.

[0129] Variations in peel strength can be obtained by changes to theheat sealing temperature, the heat sealing pressure and/or the dwelltime for sealing.

[0130] In addition to the aforementioned vinyl based lacquer systems,various other combinations of can end lacquer and heat seal coatingshave been found to be suitable for the present invention. These areexemplified, without limitation, as follows: Can lid coating (exposedside) Foil Closure coating Epoxy coating (solvent based lacquer)Polypropylene (extrusion coated) Polypropylene based heat sealed lacquerLaminated polypropylene Polypropylene formulation: extrusion coatedPolyester coated (e.g. extrusion Polyester compatible coated) heat sealcoating Polystyrene/polyester blend

[0131] It should be recognized that the combination of specific coatingformulations on the can lid (exposed side) and on the foil closurematerial (product side) needs to be carefully selected to provide thedesired combinations of peel strength and shear strength. Furthermore,the coatings must also provide adequate protection from any corrosiveattack of the metal by the product. The coatings must also comply withapplicable food/beverage contact regulations.

[0132] The coatings, at the thicknesses applied, must also be capable ofmaintaining integrity during the forming operations to which thecomponents of the lid are subjected. In particular, the coating on thelid must survive the bead curl forming operation.

[0133] It is found that coating formulations based on the classes ofcoatings listed above are able to meet all of these requirements. Aswill be seen from the above list, at least one of the two coatingformulations (and preferably both) have a thermoplastic polymer as amajor component (e.g. vinyl, polypropylene, polystyrene, polyester) andheat sealing is the preferred method of attaching the closure.

[0134] It will also be noted that the adhesion between thelacquers/coatings and the metal surfaces is important and suitablecleaning and, optionally, pretreatment of the foil surface prior tocoating is recommended.

[0135] As already stated, for the peelable closures of the presentinvention, it is desirable that the foil closure be relatively easy forthe consumer to peel back from the pouring/drinking aperture. However,it is also desirable to design the closure in such a way that theconsumer is discouraged from removing the closure foil completely, sinceit may then be discarded as litter. A preferred design of closure forthis purpose is illustrated in FIG. 15, which shows a can lid 116 havinga flat upper surface and an eccentrically disposed aperture 124surrounded by an angled flange to which a foil closure member 128 isbonded by an annular portion 146 a of a heat seal. On the side of theaperture adjacent the lid edge, the closure member has an integrallyformed pull tab 128 b (folded back over the aperture, with its unfoldedposition indicated at 128 b′). The closure member also has an integral“stay-on” extension 128 a positioned in opposed relation to tab 128 b(with respect to the aperture) and overlying the flat upper surface ofthe lid. Extension 128 a is bonded to the lid by a further heat sealportion 146 c, which is so dimensioned as to require a substantiallygreater peeling force (for separating extension 128 a from the lid) thanthat required by annular heat seal portion 146 a (for separating theclosure member from the angled flange around the aperture).

[0136] In other words, the closure member 128 of FIG. 15 includes a“stay-on” tab area or extension 128 a which is sealed to the lid panel116 by portion 146 c of the heat seal that has a size and shape whichrequires a substantially higher peel force (greater resistance topeeling) than the annular seal portion 146 a surrounding the aperture124, thereby discouraging the consumer from completely removing theclosure foil. As a result of this design, when the consumer peels openthe closure, the peel will initially be within the targeted range foreach opening, e.g. from about 2.25 lb. to 4.5 lb. (about 10-20N). Thenas the aperture is completely opened, the peel force will fall to a verylow value so that the consumer will sense that the opening is completed.If the consumer continues to pull the closure, the required peel forcewill rise rapidly to a value which exceeds the normally accepted easypeel range, i.e. to >5.5 lb. (about 25N). An example of the peelcharacteristics of a closure of this invention is given in FIG. 16.

[0137] This variation in peel force requirement can be achieved mostreadily by careful design of the seal region, in particular byappropriately selecting the dimensions of the heat seal portions 146 aand 146 c. In the case of a heat sealed closure, this is easily achievedby the design of the heat seal tooling. With a pressure sensitiveadhesive, it would be more difficult and would require the adhesive tobe printed onto the closure film in the desired pattern.

[0138]FIG. 16 is a graph showing a typical variation of peel force (90°peel test) as the closure is peeled open. As the peel is initiated, theforce rapidly increases as the foil peels away from the region of theflange on the pull tab side 128 b. As the foil is peeled from theremainder of the flange and opens the aperture, the peel force remainsfairly constant, rising to a second maximum at the end of the aperture.At this point, the foil is not sealed to the lid, and the peel forcefalls quickly to a low value. At the start of the “stay-on” extensionregion, the peel force rises to a high value to discourage the consumerfrom completely removing the closure foil.

[0139] Further control of the peel force can be obtained by varying theheat sealing conditions in the different regions of the closure. Forexample, if the temperature of the heat seal in the stay-on extensionregion were increased, a high peel strength would result. It is alsopossible to use a different heat seal lacquer, with a higher inherentpeel strength, in the “stay-on” extension region. Yet another method ofincreasing the peel force requirement in the “stay-on” tab region is bythe use of one or more ridges or other profiled features (not shown) .Such features would serve to increase the effective area of the seal andto provide a degree of mechanical keying for the closure.

[0140] As discussed above with reference to FIG. 15, the peel forcevaries as the closure is peeled back. The detailed variation of the peelforce required can be adjusted and controlled by the various methodsdescribed. The variation shown in FIG. 16 corresponds to a desirablebehavior for the consumer, in that the uniform peel force after aninitial higher start force provides ease of opening for the container;the subsequent drop in peel force gives the consumer an indication (byfeel) that the aperture is completely opened; and, finally, the rapidrise of the force due to the “stay-on” extension signals the consumerthat the closure is intended to stay on and be folded back for drinking.

[0141] With an aluminum foil closure material, employing a “stay-on”arrangement as described, the closure can be easily folded down so thatit does not significantly interfere with the drinking experience of theconsumer. Furthermore, since the foil has good dead-fold characteristics(i.e. it does not exhibit any noticeable spring back), the closure canbe folded back over the aperture if desired. Although this does notreseal the can, it would prevent the undesired ingress of dirt orinsects into the beverage between drinks, and may also reduce thespillage if a can is accidentally tipped.

[0142] Yet another advantageous feature of the invention, in particularembodiments as illustrated in FIGS. 17-20, is the incorporation of asource of a fragrance or aroma in the can lid, so that peeling of theclosure member to open the can also acts to expose a small quantity ofan oil or wax based aroma concentrate, located on the lid in a positionwhich is in close proximity to the nostrils of a person drinking fromthe can aperture. The aroma is selected to enhance or complement thetaste of the beverage.

[0143] It is well known that the senses of smell and taste are closelyrelated, and in particular that the sense of smell can significantlyenhance the taste experience. Preservation or enhancement of a smellassociated with a particular beverage, thereby improving the aroma ofthe product, may serve to increase the overall enjoyment of the product.Fragrances which may be thus provided may include (by way of nonlimitingillustration) lemon, orange, lime, mint, etc.

[0144] The aroma-enhancing feature may, for example, advantageously beincorporated in a can lid 116 having a “stay-on” foil closure member 128as described above with reference to FIGS. 15-16. A small part of thelid area, initially covered by the foil closure member (FIG. 17A) butexposed upon peeling of the closure member (FIG. 17B), is modified so asto receive a small quantity 156 of an oil- or wax-based fragrance. Thiscan be achieved by forming a small upwardly opening depression orreservoir 158 in the lid 116 (FIG. 18) and/or by forming a similarreceptacle indentation (facing the lid; not shown) in the foil closuremember itself.

[0145] The reservoir, and hence the supply of fragrance, are disposed onthe side of the aperture 124 away from the edge of the lid so as to beclose to the nostrils of a person drinking from the can. This locationis between the aperture 124 and the stay-on heat seal portion 146 c andis thus covered by the closure extension 128 a when the closure memberis sealed on the lid.

[0146] A wide variety of concentrated fragrances are readily availableand, for the described use, the volume required is about one drop (lessthan 0.01 ml). Since the fragrance is sealed between the lid 116 and theclosure member 128, there is little if any loss of fragrance duringstorage, owing to the excellent barrier properties of aluminum.

[0147] When the foil closure member is peeled back (FIG. 17B) to openthe can it exposes the fragrant oil 156, releasing the aroma. As will beapparent from the drawings, the fragrance reservoir 158 is positioned onthe can lid in close proximity to the nose of a person drinking straightfrom the can, to maximize the effectiveness of the aroma.

[0148] For use with a lid having a fragrance reservoir, the heat seal146 securing the closure member 128 to the lid 116 is configured tofully surround the reservoir 158 containing the supply of fragrance. Twospecific heat seal designs for this purpose are respectively shown inFIGS. 19 and 20. In FIG. 19, the heat seal area 146 a around theaperture 124 is contiguous with the heat seal area 146 b surrounding thefragrance reservoir or well 158 and the heat seal portion 146 c thatsecures the “stay on” extension 128 a of the closure member to the lid;the design is such that as the lid is peeled back from the aperture,there is a high probability that the fragrance-containing depression 158in the lid will be partially or fully exposed and the fragrance willstart to be released. In FIG. 20, the heat seal area 146 d surroundingthe fragrance containing reservoir is isolated from the heat sealportions 146 a (around the aperture) and 146 c (bonding the stay-onclosure member extension to the lid) , but again, the action of peelingback the closure member results in partial or complete opening of thereservoir to release the fragrance. In the case of FIG. 20, by isolatingthe fragrance reservoir 158 from the main heat seal areas 146 a and 146c, the probability of premature evaporation of the fragrance owing toheat input from the heat sealing tools is significantly reduced.

[0149] In brief summary, the present invention provides a novel can endwith a safe and convenient aperture and a heat sealable foil closure,suitable for use with carbonated beverages or similar products. Amongthe benefits and advantages that may be achieved with the cans of theinvention are the following:

[0150] improved sanitary characteristics, because no external exposedsurface is introduced into the beverage, as occurs when present-dayscored lids are opened with a riveted pull-tab system;

[0151] enhanced aesthetics, in that the peelable foil closure can beembossed and printed (inside and/or outside);

[0152] increased selection of aperture size and shape since, while therewill be some limitations, a wider range of aperture sizes and shapeswill be possible than is the case with present-day scored lids;

[0153] greater safety, in particular because the reverse curl of theaperture-defining bead eliminates sharp edges;

[0154] ease of opening, and concomitant consumer satisfaction, sincemarketing studies in the food industry indicate that consumers prefereasy-peel closures to the scored ends of present-day carbonated beveragecans as well as to the use of can openers;

[0155] ease of use, since a can with this end design has better pouringcharacteristics and may be easier to drink from directly.

[0156] Especially preferred embodiments of the invention are carbonatedbeverage cans with readily peelable closure members characterized by aburst resistance of at least about 90 psi (or higher, e.g. 100 psi orabove) and a shelf life of at least six months or more. The creepresistance and barrier properties of foil closures, together with theshear strength of heat seals, enable attainment of the desired extendedshelf life.

[0157] Still further features and advantages of the invention reside inthe provision of cans with lids having the above described angled flangeaperture and heat sealed closure member, wherein the lid diameter(hence, also, the lid area) is smaller than that of present-dayconventional cans with riveted tabs and scored areas for opening, yetwithout any reduction in the size of the opening for pouring and/ordrinking.

[0158] In recent years, the diameter of the can end (lid) used forcarbonated and noncarbonated beverages has been significantly reduced.Most recently the size has been reduced from “204” size (about 2¼ inchesin diameter) to “202” size (about 2⅛ inches in diameter). This sizereduction alone represents a significant potential saving to can makersand fillers. However, a number of additional benefits can also berealized as a result of this size reduction.

[0159] For example, it is well known that a reduced diameter lid is lesssusceptible to buckling under the internal pressure. This can beexploited in a number of ways (the choice or combination depending oneconomic, aesthetic and other (e.g., hygiene, recycling, etc.)considerations. Essentially, a reduced lid diameter enables the lidprofile design, alloy, temper and gauge to be reconsidered.

[0160] Furthermore, the smaller size means that adequate buckle strengthcan be achieved with a thinner gauge. For “204” size ends, the typicalgauge was about 0.009 inch and for “202” ends, the gauge requirement isabout 0.0086 inch.

[0161] As mentioned above, AA 5182, the currently preferred lid alloy,is a premium alloy (due to the Mg content) and is costly and difficultto roll. Moreover, for can end (lid) applications, the sheet must becoated on both sides. For these reasons, there is a significant economicincentive for can makers to reduce the lid size and gauge as much aspossible.

[0162] The trend for cans to have larger opening ends (LOE) means that,with conventional riveted tab lids, the opportunity for furtherreduction in end diameter is very limited, since the tab and thecentrally positioned rivet require the lid to be of a certain minimumdiameter.

[0163] By use of the angled flange aperture and heat sealed foil closuresystem of the present invention, the lid diameter can be significantlyreduced (e.g. to below 2 inches in diameter), while still retaining alarge pouring opening. The reduction in lid diameter also enables thegauge of the lid to be further reduced (or, alternatively, enables useof a lower strength and lower cost alloy), since buckle resistance iseasier to achieve with a smaller diameter lid.

[0164] With this approach, it should be possible to reduce the can enddiameter by at least 5% to the “200” size (about a 10% area reduction,compared to the current “202” size), with an additional reduction ofabout 5% in gauge (to a gauge of less than 0.0082 inch) , while stillmeeting the target buckle resistance of the can lid. Thereby significantsavings in metal may be achieved, although an extra necking stage mustbe incorporated into the can body making operation to conform the upperend of the can body dimensionally to the reduced-diameter lid, adding anexpense that would partially offset the cost savings.

[0165] The reduction in can lid diameter attainable with the inventionalso affords opportunities to reduce or eliminate the “countersink”feature of the can lid, which is advantageous, since the countersink(formed around the periphery of the lid) is prone to contamination bydust or debris. FIG. 21 illustrates a lid 160 embodying the inventionand free of countersinking, i.e., having no peripheral countersink (suchas is shown, for example, at 162 in each of FIGS. 12 and 18); thesubstantially planar upper surface 164 of the lid extends all the way tothe raised annular rim 166. It will also be recognized that thereduction or elimination of the countersink feature also reduces themetal usage (by up to about 5%), providing further potential costsavings.

[0166] It should be noted that, where it is desired to be able to stackcans on each other, a smaller diameter lid may require some redesign ofthe can body. In previous can designs, the bottom profile has beendesigned to stack against the lid. However, as lid diameters havedecreased, it is becoming more difficult to achieve this. With thecurrent “202” size lid, the can bottom design has been modified toachieve this stackability. However, the narrowing of the base isapproaching the point where the stability of the can (to tipping) isbecoming a concern. If the lid is further reduced in size it maytherefore be necessary to redesign the can base further to enable stablestacking.

[0167] FIGS. 22-24 illustrate a specific embodiment of the invention ina beverage can including a one-piece can body 170 with a narrow neck 172and a reduced-diameter can end or lid 174 (which has an angled flangeaperture 176 and foil bonded heat sealed closure 178) with nocountersink or recess.

[0168] The domed bottom 180 and sidewall 182 of the body 170 are formedwith the draw and iron procedure currently in widespread use. The canbody sidewall is then necked as shown at 172 to a small diameter ofapproximately 1 to 1.5 inches, and flanged to enable attachment of thelid 174. After the can is filled, the small diameter lid with thepeelable foil bonded closure 178 as described above is seamed to theopen upper end of the necked can.

[0169] The main purpose of the countersink in current can lid designs isto minimize deflection and also to reduce the probability of buckling orreversal of the can end under internal pressure. In the embodiment ofFIGS. 22-24, the lid has a small diameter, and therefore will notdeflect as much as a larger diameter end would. For that reason, thereis no need for a recess or countersink. Since there is no countersink orrecess, can end failure will not involve buckling. The maximum internalpressure for the end will be determined by the strength and gauge of thecan end and the foil closure material, the bonding strength between thefoil and end, and the seam integrity. Hence the can end material can bemade from much lower gauge metal than that (e.g. AA 5182) which iscurrently used. The alloy used could also be the same as that used forthe can body, for instance, AA 3104 alloy.

[0170] The narrow neck 172 gives the can a bottle shape, which may bepreferred by many consumers for aesthetic reasons, especially if thisshape is enhanced with graphics and/or embedded design elements (notshown).

[0171] Illustrative dimensions of the can of FIG. 22 include a maximumcan body diameter (bottom portion) of 2.60 inches, a neck taperingupwardly to receive a lid having an outer diameter of 1.56 inches, andan aperture with a diameter of 0.75 inch, the overall height of the canbeing 6.50 inches.

[0172] Another exemplary embodiment of the invention in a necked canwith a reduced diameter lid 188 having an angled flange aperture andheat sealed closure is shown in FIG. 25. The can comprises a body 190with an integral neck 192. The base of the container consists of a panel194 similar to a conventional can lid (but lacking any rivet, tab,scored area or other opening system) and is seamed onto the open lowerend of the can body in the same way as conventionally utilized to join alid to the upper end of a drawn and ironed can body.

[0173] The forming of the body 190 may be understood by reference to thecan body maker tooling shown in FIG. 26 and the alternativemodifications thereof respectively illustrated in FIGS. 27 and 29. FIG.26 shows, in simplified schematic cross-section, a standard can bodymaker (known in the prior art) comprising a hollow mandrel 200 with ashaped end cap 202, a series of ironing rings 204 a, 204 b, 204 c, and a“domer” 206. The domer and the shaped end of the mandrel are designed togenerate the familiar outwardly concave can bottom dome profile. Thiscan body making operation results in a significant thinning of the metalsidewalls due to the ironing process, but the thickness of the metal inthe bottom of the can is not significantly reduced.

[0174]FIG. 27 shows one modification for producing the body of the canof FIG. 25. The features of particular significance are the domer tool208 which is designed to generate the neck 192 of the new can body 190,and the end cap 210 of the mandrel 212 which is shaped so as to matchthe shape of the domer tool (allowing a suitable clearance).

[0175] The detailed shape of this tooling is optimized so as to controlmetal flow during the forming operation, and to minimize the likelihoodof metal failure (tearoffs and the like). In particular, small radii ofcurvature are avoided and the extent of the deformation is kept to aminimum consistent with the requirements for a neck. The neck 192 itselfis slightly tapered so that the finished body 190 can be easily removedfrom the mandrel 212. The can body 190, complete with neck 192, is shownin FIG. 28.

[0176] With this formed shape as a starting point, a number ofadditional steps are employed to produce the final can of FIG. 25. Theadditional steps include trimming or punching an opening in the upperend of the neck 192 to constitute an open upper end of the can body, onwhich the lid 188 is to be secured; trimming the other end 214 of thecan to remove earing scrap; and attaching a plain metal can end shell194 to the latter end by a seaming operation. The can body is thenfilled, for example with a carbonated beverage, and the lid 188 with itsangled flange aperture and heat sealed closure member is secured to theopen upper end of the neck 192.

[0177] In addition to this preferred method, two alternative processesfor producing the modified can body will be described. In the firstalternative, the can body 190 with formed neck 192 is produced using adouble action forming process shown schematically in FIG. 29. Thefeatures of particular significance are that the domer tool of FIG. 27is replaced by a tool 220 which is designed to generate the neck of thenew container (as before), and the end cap of the mandrel is replaced byan annular piece 222. In the center of this a second movable tool 224 isintroduced so the complete configuration operates as a double actionpress tool, with the outer annular portion generating the outer profileof the neck region, and the inner tool applying an additional secondforming step to form the neck of the can body. The press itself needs tobe modified to give the appropriate “double action” operation (doubleaction presses and forming operations are well known in, for example,the cup forming process). The additional steps for trimming, forming ofthe opening and application of the can bottom end and lid would besimilar to those described in the preferred method.

[0178] The second alternative method (not illustrated in the drawings)involves the production of a modified can body with a convex domed end,by a standard drawing and ironing process and a subsequent hydroformingoperation similar to that described by Belvac Production Machinery Inc.,Lynchburg, Va., for shaping of can walls. This hydroforming processinvolves the use of a high pressure jet of fluid such as water and ashaped mold, to complete the forming of the neck region of the can. Byusing a split mold, the sidewall could optionally be shaped fordecorative purposes.

[0179] It should be recognized that embodiments such as that of FIG. 25may offer the following advantages:

[0180] The can body and neck are formed in a single high speed processand can utilize existing can body makers (with different tooling).

[0181] The neck is formed from metal which has not been thinned by theironing process.

[0182] Although some re-tooling would be required, it should berelatively straightforward to modify filling lines to handle cans ofthis design, since they would be similar in shape to glass or PETbottles.

[0183] It will be recognized that this design and process will requirechanges to the tooling and container handling and inspection systems.However added costs due to these factors will, partly or completely, beoffset by the savings listed above.

[0184] Although omission of the countersink from the lid has beendescribed above for embodiments of the invention having lids of reduceddiameter as compared to the conventional lid size represented by a 202can, the invention more broadly contemplates the reduction orelimination of the countersink from cans having lids of conventional 202size (i.e., a lid diameter of 2.25 inches) as well as smaller diameters.The countersink, though contributing to overall stiffness and resistanceto buckling, is undesirable because any dirt or spillage on the lidtends to collect in the countersink; also, its presence in a lid designincreases the metal required for the lid. The annular flange-peelableclosure opening arrangement of the can lid of the invention, incombination with a suitable choice of alloy and gauge, enables reductionor elimination of the countersink. In such case, since the countersink(when present) contributes to the overall stiffness and resistance tobuckling of the lid, additional stiffening features such as raised ordepressed ribs, coined areas, or raised or depressed panel areas may beformed in the lid.

[0185]FIG. 30A, corresponding in pertinent respects to FIG. 18, shows acan lid 316 a embodying the invention, including an aperture 324 closedby a peelable closure member 328 and defined by an upwardly projectingannular flange 330, having a countersink 362 a of conventional shape anddimensions, e.g. about 0.090 inch deep (dimension d₁) in the case of a202 can lid. FIG. 30B shows a similar can lid 316 b in which the depthd₂ of the countersink 362 b has been reduced by two-thirds (to 0.030inch) as compared to d₁ in FIG. 30A, and the width of the countersinkhas also been lessened. This small countersink provides a degree ofstiffening and buckle resistance but, if sufficiently shallow (anexemplary or currently preferred range being a depth of 0.015 to 0.030inch), is less likely to accumulate dust and debris. FIG. 30C,corresponding in pertinent respects to FIG. 21, shows another similarcan lid 316 c in which the countersink has been entirely eliminated; inits place is a planar annular region 362 c.

[0186] The choice of depth of the reduced countersink 362 b (FIG. 30B)may in practice be based on consumer perception, providing the deepestpossible countersink that does not attract negative attention on thepart of consumers. Once a countersink depth has been established, lidgauge, alloy and other design modifications such as added stiffeningfeatures are selected to assure adequate buckle resistance.

[0187] Examples of types of stiffening features that may be formed incan lids for such purposes are illustrated in FIGS. 31A-31E, wherein thecan lid is designated 316. These features include a depressed rib 364(FIG. 31A), typically 0.03 inch deep and 0.05 inch wide; a raised rib366 (FIG. 31B); a raised panel area 368 (FIG. 31C) with a sloped areaabout 0.03 inch wide and a raised area is about 0.03 inch high; adepressed panel area 370 (FIG. 31D); and a coined area 372 (FIG. 31E).The coined area is thinned, with slightly thickened regions along itsedges; a typical illustrative width of a coined area is 0.03 inch butthis dimension can vary considerably.

[0188]FIGS. 32A and B, 33A and B, and 34A and B illustrate variousspecific exemplary combinations of these features to enhance stiffnessand buckle resistance in 202 can lids (each having a diameter of 2.25inches, and respectively designated 316D, 316E and 316F), embodying theinvention, and in which countersinks have been eliminated as indicatedat 362 c. The stiffening features are identified by the same respectivereference numerals as in FIGS. 31A-31E. In FIGS. 32A and B and 33A andB, the peelable closure member 328 a has a circular periphery; in FIGS.34A and B, the aperture 324 a has a shape similar to current can endapertures known in the trade as LOE (Large Opening Ends). Manyvariations of the illustrated arrangements are possible.

[0189] By way of further illustration of the invention, reference may bemade to the following specific examples, in which Example 1 is ahypothetical example and Examples 2 and 3 describe burst resistancetests performed on actual samples of can lids with heat-sealed closuresembodying features of the invention, while Example 4 describes actualtests related to shelf life. In these Examples, identifications ofaluminum alloys by four-digit numbers with the prefix “AA” refer todesignations of aluminum alloy compositions registered with the AluminumAssociation, as will be understood by persons skilled in the art.

EXAMPLE 1

[0190] An illustrative can end (lid) embodying the present inventionwith a heat sealed foil/polymer laminate closure might be constructedwith the following specification: Aperture diameter (A): 1″ Flangeangle: 20-25° Laminate: .004″ foil (AA 3104) + .001″ polymer (e.g.,polyethylene, polypropylene, polyester) Heat seal width: 0.1″ Can lidsheet: 0.009″ (AA 5182 alloy) with a heat sealable coating

[0191] It will be understood that a range of values for each parametershould be possible. The target burst resistance for such a lid wouldbe >90 psi and the target peel force (at 90° to the plane of theaperture) would be <4 lbs.

EXAMPLE 2

[0192] Tests were performed to determine peel strength and burstresistance for can ends (lids) of “202” can end size (a standard cansize designation) in accordance with the invention, having an annularfrustoconical flange with an 18° angle of slope defining an aperture ¾″in diameter, covered by a foil closure heat sealed to the flange aroundthe aperture. The lids were formed from can end sheet of AA5182 aluminumalloy at a gauge of 0.0086″, and their outer surfaces were coated with“Valspar” unicoat at a coating weight of 1.5 mg/in² (approximately 1.5μthick). The closures were made from heat sealable stock of 50μ foil ofAA3105 aluminum alloy, coated on its inner surface (the surface incontact with the aperture-defining frustoconical flange) with RorschachTH388 vinyl heat seal lacquer at a coating weight of 6 g/m² (about 6μthick). Heat sealing was performed at various selected tool temperatures(on the side of the foil closure) of from 230° to 280° C., with apressure of 975 N and a time of 0.3 sec.

[0193] Initially, to determine peel strength, T-peel test pieces wereprepared from the can end sheet and heat sealable foil stock describedabove by heat sealing 15 mm wide strips of the foil stock to 15 mm widecan end sheet samples for different heat seal temperatures (as listed inFIG. 10). Results, summarized in FIG. 10, show that the peel strengthcan be adjusted for this combination of materials by modifying the heatseal temperature. As mentioned above, a peel force of between about 10 Nand about 15 N is generally regarded as acceptable for an easy openingcontainer. Since the anticipated width of the heat seal for closuresembodying the present invention may be typically or convenientlyapproximately 15 mm, the peel forces will fall within this acceptablerange.

[0194] To test burst resistance, a number of formed and heat sealed canends as described were subjected to a standard burst test in which therim of the can end is clamped to a rubber gasket seal and a graduallyincreasing air pressure is applied to the inner lid surface. Thedeformation of the lid and seal can be observed during the test and themaximum pressure at failure is recorded. After testing the lids areexamined to determine the mode of failure.

[0195] The results of these burst tests are shown in FIG. 11. For thesetests, burst pressures of approximately 60 psi were recorded. During thetests it was noted that the foil closure 28 stretched and “domed” to apoint where the tension in the foil had developed a significant peelcomponent, i.e., the tangent (in a vertical plane) to the bulged foilclosure 28 at the edge of the aperture 24 exceeded the 18° slope angleof the flange 30, as illustrated diagrammatically in FIG. 9. Failure ofthe seal occurred by a peel initiated at the inner edge of the aperture.

[0196] A 60 psi burst resistance is sufficient for low levels ofcarbonation or for normally carbonated beverages under standardconditions of use. However, since carbonated products must be capable oftolerating varying degrees of extreme conditions (elevated temperature,agitation, etc.), the normal targeted burst resistance is generally 90psi or higher. In the case of the materials employed in this Example,higher burst resistance should be achieved with this gauge of foil if ahigher flange angle (e.g. 25°) were to be used.

EXAMPLE 3

[0197] A further series of can ends in accordance with the inventionwere prepared and tested. The lid members were the same (dimensions,gauge, alloy, coating, flange slope angle and aperture diameter) as inEXAMPLE 2, but the closures were made of heat sealable foil stock of 70μfoil of AA9802 aluminum alloy with an inner surface coated with a vinylheat seal lacquer of unknown formulation. Heat sealing was performedwith a tool temperature (on the foil closure side) of 280° C., under thesame pressure and time conditions as in EXAMPLE 2.

[0198] These materials (can end sheet and foil closure) were subjectedto peel strength testing. Peel strengths of greater than 20 N/15 mm wererecorded for these samples. This is too high for convenient peeling andindicates that the vinyl lacquer was not a suitable formulation.

[0199] Samples of the lids and closures were formed, subjected to heatsealing, and tested for burst resistance. Burst resistance was found tobe >90 psi. During the burst tests, the foil closures bulged to form ashallow dome, but the distortion was not sufficient to create asignificant peel component to the resultant tension force.

[0200] Failure of the lids eventually occurred by distortion of the canend shell metal. The foil and the heat seal survived the testsatisfactorily.

[0201] With the thicker foil of this Example, the doming which occurs atpressures below 90 psi (for the 3/4″ aperture) was below the level atwhich a peel component of force would arise.

EXAMPLE 4

[0202] A further series of can ends in accordance with the inventionwere prepared and tested. The lid members differed from those ofEXAMPLES 2 and 3 in having a flange slope angle of about 23° and anaperture diameter of ⅞″. The can end lacquer was Valspar Unicoat (vinylbased) lacquer as before, at a thickness of between 1.5 and 2μ. Theclosures were made of heat sealable foil stock of 80μ gauge foil ofAA3104 aluminum alloy with an inner surface coated with apolystyrene/polyester blend heat seal lacquer designated TH312 (AlcanRorschach) applied at 8 g/m². Heat sealing was performed with a top tooltemperature of 200° C., a bottom tool temperature of 200° C., a dwelltime of 0.3 second, and a heat seal width of 0.079 inch (2 mm). Heatsealing was carried out before the angled flange was formed.

[0203] Burst tests were performed on the lids. In tests performed beforethe angled flange was formed, failure of the heat seal occurred atbetween 40 and 55 psi. In tests performed after forming the flange,using a standard can end bulge test, failure by buckling of the can endoccurred at between 85 and 90 psi. In tests also performed after formingthe flange but using a modified clamping tool to prevent end buckling,failure of the heat seal occurred between about 110 psi and 120 psi (thelowest value recorded was 106 psi).

[0204] Peel strength was tested using a 90° peel test. The peel forcevaried during the test but was within the range between about 2½ lbs(≈11.3 Newtons) and 4 lbs (≈18 Newtons).

[0205] To test shelf life, can ends of this Example were used for cansfilled with carbonated soft drinks at an estimated filling pressure of≈60 psi and stored at ambient temperature. Samples prepared and testedin this way have maintained full pressurization for over six months.

EXAMPLE 5

[0206] The shelf life of cans in accordance with the invention wastested by preparing a can having a lid in accordance with the invention,including an angled flange having an 18° angle of slope and defining acircular aperture 0.750 inch in diameter. The closure was aluminum foil0.004 inch (100μ) thick, with a vinyl/acrylic lacquer (“TH 388”) usedfor the heat seal, which had a width of 0.079 inch (2 mm). The internalpressure of the can was 50 psi. The can was examined weekly for overeight weeks. Throughout this period, there were no detectable changes inbulge height of the foil closure and there was no detectable change inthe heat seal joint (i.e., no sliding).

[0207] In a further test, another can was prepared, having a lid inaccordance with the invention, including an angled flange having an 18°angle of slope and defining a circular aperture 0.875 inch in diameter.The closure was aluminum foil 0.004 inch (100μ) thick, with avinyl/acrylic lacquer (“TH 388”) used for the heat seal, which had awidth of 0.079 inch (2 mm). The internal pressure of the can was 60 psi.The can was examined weekly for over six weeks. Throughout this period,there was no change in bulge height of the foil closure and nodetectable change in the heat seal joint (i.e., no sliding).

[0208] It is to be understood that the invention is not limited to thefeatures and embodiments hereinabove specifically set forth, but may becarried out in other ways without departure from its spirit.

What is claimed is:
 1. A can comprising: (a) a metal can body having anopen upper end; (b) a substantially rigid metal can lid secured at itsperiphery to and closing said can body end, said lid having an uppersurface; (c) an annular flange formed in a portion of said lid andprojecting upwardly from said lid upper surface, said flange having anupwardly sloping outer surface and an annular inner edge lyingsubstantially in a plane and defining an aperture with an averagediameter between about 0.625 inch and about 1 inch; and (d) a flexibleclosure member of a material comprising a metal foil, extending entirelyover said aperture and peelably bonded by a heat seal to said flangeouter surface entirely around said aperture.
 2. A can as defined inclaim 1, wherein said can has a geometric axis, said lid upper surfaceis substantially flat, said aperture is circular and said flange isdisposed in a portion of said lid eccentric to said geometric axis.
 3. Acan as defined in claim 1, wherein said closure member and heat sealhave a tear/shear force resistance of at least about lb./in., andwherein said average diameter of said aperture and the upward slope ofsaid flange are mutually selected such that when the closure member issubjected to differential pressure of a given value between about 50 andabout 100 p.s.i. within the can, the tear/shear force exerted on theclosure member and heat seal does not exceed said tear/shear forceresistance.
 4. A can as defined in claim 3, wherein said tear/shearforce resistance is between about 25 and about 75 lb./in.
 5. A can asdefined in claim 47, wherein said closure member material is deformable,and wherein said average diameter of said aperture, said angle of slopeof said flange, and the deformability of said material are mutuallyselected such that said closure member, when subjected to differentialpressures up to at least about 90 p.s.i. in the can, bulges upwardlywith an arc of curvature such that a line tangent to said arc at saidinner edge of said flange lies at an angle to said plane notsubstantially greater than said angle of slope of the flange outersurface.
 6. A can as defined in claim 47, wherein said closure membermaterial is deformable, and wherein said average diameter of saidaperture, said angle of slope of said flange, and the deformability ofsaid material are mutually selected such that said closure member, whensubjected to differential pressures up to at least about 100 p.s.i. inthe can, bulges upwardly with an arc of curvature such that a linetangent to said arc at said inner edge of said flange lies at an angleto said plane not substantially greater than said angle of slope of theflange outer surface.
 7. A can as defined in claim 1, wherein saidclosure member and heat seal have a tear/shear force resistance of atleast about 75 lb./in., and wherein said average diameter of saidaperture and the upward slope of said flange are mutually selected suchthat when the closure member is subjected to differential pressure ofnot more than about 90 p.s.i. within the can, the tear/shear forceexerted on the closure member and heat seal does not exceed saidtear/shear force resistance.
 8. A can as defined in claim 1, whereinsaid closure member and heat seal have a tear/shear force resistance ofat least about 75 lb./in., and wherein said average diameter of saidaperture and the upward slope of said flange are mutually selected suchthat when the closure member is subjected to differential pressure ofnot more than about 100 p.s.i. within the can, the tear/shear forceexerted on the closure member and heat seal does not exceed saidtear/shear force resistance.
 9. A can as defined in claim 47, whereinsaid closure member and heat seal have a tear/shear force resistance ofat least about 75 lb./in., and wherein said average diameter of saidaperture and said angle of slope of said flange are mutually selectedsuch that when the closure member is subjected to differential pressureof not more than about 90 p.s.i. within the can, the tear/shear forceexerted on the closure member and heat seal does not exceed saidtear/shear force resistance.
 10. A can as defined in claim 6, whereinsaid closure member and heat seal have a tear/shear force resistance ofat least about 75 lb./in., and wherein said average diameter of saidaperture and said angle of slope of said flange are mutually selectedsuch that when the closure member is subjected to differential pressureof not more than about 100 p.s.i. within the can, the tear/shear forceexerted on the closure member and heat seal does not exceed saidtear/shear force resistance.
 11. A can as defined in claim 1, whereinsaid heat seal has a 90° peel strength between about 8 N and about 20 N.12. A can as defined in claim 1, wherein said annular inner edge isformed with a reverse bead curl.
 13. A can as defined in claim 12,wherein said reverse bead curl is substantially tangent to the upwardlysloping outer surface of the flange.
 14. A can as defined in claim 1,wherein said metal foil is aluminum alloy foil.
 15. A can as defined inclaim 14, wherein said aluminum alloy foil has a thickness between about0.003 inch and about 0.004 inch.
 16. A can as defined in claim 1,wherein said heat seal is formed as an annulus surrounding said apertureand having a width between about 0.079 inch and about 0.118 inch.
 17. Acan as defined in claim 1, wherein said closure has a tab portion with amanually graspable free end and an extension overlying said lid inopposed relation to said tab portion, said heat seal including anannulus surrounding said aperture and a further seal portion bondingsaid extension to said lid such that the peel force required to separatethe extension from the lid is greater than that required to separate theclosure member from the lid at the annulus, whereby the aperture can beopened by peeling back the closure member while the closure memberremains secured to the lid by said further seal portion.
 18. A can asdefined in claim 17, including a body of fragrance-providing materialdisposed between the closure member and the lid and surrounded by theheat seal such that when the closure member is subjected to a peel forceeffective to open the aperture, the body of fragrance-providing materialbecomes exposed.
 19. A can as defined in claim 1, including a body offragrance-providing material disposed between the closure member and thelid and surrounded by the heat seal such that when the closure member issubjected to a peel force effective to open the aperture, the body offragrance-providing material becomes exposed.
 20. A can as defined inclaim 1, wherein said body is a drawn and ironed metal can body forholding a carbonated beverage; wherein the lid is formed with aperipheral rim engaging the open upper end of the can body andprojecting upwardly above the upper surface of the lid; wherein the bodyis formed with an outwardly concave lower end, the rim and body lowerend being mutually shaped and dimensioned to permit stable verticalstacking of the can with other identically shaped and dimensioned cans;wherein the flexible closure member is domed so as to rise to a heightabove the annular flange; and wherein the height of the rim, theconcavity of the body lower end, and the height to which the closurerises above the annular flange are such that there is sufficientclearance between the lid upper surface of the can and the concavebottom of another identical can stacked above it to accommodate thedomed closure.
 21. A can lid member mountable on a metal can body havingan open upper end so as to be secured at its periphery to and to closesaid can body end, said lid comprising a substantially rigid unitarymetal member having an upper surface with an annular flange formed in aportion of said lid and projecting upwardly from said lid upper surface,said flange having an upwardly sloping outer surface and an annularinner edge lying substantially in a plane and defining an aperture withan average diameter between about 0.625 inch and about 1 inch, saidflange being arranged and configured to be closed by a flexible closuremember extending entirely over said aperture and peelably bonded to saidflange outer surface around said aperture.
 22. A can lid mountable on ametal can body having an open upper end so as to be secured at itsperiphery to and to close said can body end, said lid comprising asubstantially rigid unitary metal can lid member having an upper surfacewith an annular flange formed in a portion of said lid and projectingupwardly from said lid upper surface, said flange having an upwardlysloping outer surface and an annular inner edge lying substantially in aplane and defining an aperture with an average diameter between about0.625 inch and about 1 inch; and a flexible metal foil closure memberextending entirely over said aperture and peelably bonded by a heat sealto said flange outer surface entirely around said aperture.
 23. Acarbonated, or otherwise pressurized, beverage package comprising: (a) acan including a metal can body having an open upper end and asubstantially rigid metal can lid secured at its periphery to andclosing said can body end, said lid having an upper surface; (b) a bodyof a carbonated, or otherwise pressurized, beverage contained withinsaid can; (c) an annular flange formed in said lid and projectingupwardly from said lid upper surface, said flange having an upwardlysloping outer surface and an annular inner edge lying substantially in aplane and defining an aperture with an average diameter between about0.625 inch and about 1 inch; and (d) a flexible metal foil closuremember extending entirely over said aperture and peelably bonded by aheat seal to said flange outer surface entirely around said aperture.24. A method of producing a can containing a carbonated, or otherwisepressurized, beverage, comprising: (a) filling a drawn and ironed metalcan body, having an open upper end, with a carbonated, or otherwisepressurized, beverage, and (b) closing said open upper end of said canbody by securing a substantially rigid metal can lid at its periphery tosaid can body end, said lid having an upper surface and an annularflange formed in said lid and projecting upwardly from said lid uppersurface, said flange having an upwardly sloping outer surface and anannular inner edge lying substantially in a plane and defining anaperture with an average diameter between about 0.625 inch and about 1inch, and a flexible metal foil closure member extending entirely oversaid aperture and peelably bonded by a heat seal to said flange outersurface entirely around said aperture.
 25. A can for holding liquid,comprising: (a) a metal can body having an open upper end; (b) asubstantially rigid metal can lid peripherally secured to and closingsaid can body end, said lid having an upper surface and defining anaperture therein for pouring or drinking liquid from the can; and (d) aflexible closure member extending entirely over said aperture andpeelably bonded by a heat seal to said lid entirely around saidaperture; wherein the improvement comprises: (e) said closure includinga tab portion with a manually graspable free end and an extensionoverlying said lid in opposed relation to said tab portion, said heatseal including an annulus surrounding said aperture and a further sealportion bonding said extension to said lid such that the peel forcerequired to separate the extension from the lid is greater than thatrequired to separate the closure member from the lid at the annulus,whereby the aperture can be opened by peeling back the closure memberwhile the closure member remains secured to the lid by said further sealportion.
 26. A can for holding liquid, comprising: (a) a metal can bodyhaving an open upper end; (b) a substantially rigid metal can lidperipherally secured to and closing said can body end, said lid havingan upper surface and defining an aperture therein for pouring ordrinking liquid from the can; and (d) a flexible closure memberextending entirely over said aperture and peelably bonded by a heat sealto said lid entirely around said aperture; wherein the improvementcomprises: (e) a body of fragrance-providing material disposed betweenthe closure member and the lid and surrounded by the heat seal such thatwhen the closure member is subjected to a peel force effective to openthe aperture, the body of fragrance-providing material becomes exposed.27. A can as defined in claim 1, wherein the can lid is formed of thesame alloy as the can body.
 28. A can as defined in claim 27, whereinsaid alloy is AA3104 alloy or AA 3004 alloy.
 29. A can as defined inclaim 1, wherein the can lid is formed of AA3104 alloy or AA 3004 alloy.30. A can as defined in claim 1, wherein the can lid is formed of steel.31. A can as defined in claim 1, wherein the can lid has a diameter ofless than two inches.
 32. A can as defined in claim 31, wherein the canlid has a gauge of less than 0.0082 inch.
 33. A can as defined in claim31, wherein the can lid is substantially free of countersinking.
 34. Acan comprising: (a) a metal can body having an open upper end, a lowerportion with a maximum diameter and an upper portion formed as a neck ofreduced diameter relative to said maximum diameter; (b) a substantiallyrigid metal can lid secured at its periphery to and closing said canbody end, said lid having an upper surface; (c) an annular flange formedin a portion of said lid and projecting upwardly from said lid uppersurface, said flange having an upwardly sloping outer surface and anannular inner edge lying substantially in a plane and defining anaperture; and (d) a flexible closure member of a material comprising ametal foil, extending entirely over said aperture and peelably bonded bya heat seal to said flange outer surface entirely around said aperture.35. A can as defined in claim 34, wherein said body is a drawn andironed metal can body having an initially cylindrical sidewall with anupper portion, and wherein said neck is produced by forming saidsidewall upper portion.
 36. A can as defined in claim 34, wherein saidbody is a drawn and ironed metal can body having a generally cylindricalsidewall, an initially closed end portion integral therewith, and anopen second end; wherein said neck is produced by forming said endportion; wherein said open second end is closed by seaming a can endthereto; and wherein said open upper end is produced by forming anendwise opening in said neck.
 37. A can as defined in claim 1, whereinthe annular flange is frustoconical.
 38. A can as defined in claim 1,wherein the can lid is substantially free of countersinking.
 39. A canas defined in claim 38, wherein the can lid is formed with stiffeningfeatures.
 40. A can as defined in claim 39, wherein said stiffeningfeatured are selected from the group consisting of raised ribs,depressed ribs, raised panel areas, depressed panel areas and coinedareas.
 41. A can as defined in claim 1, wherein the can lid has adiameter of about 2.25 inches and a countersink not more than about 0.03inch deep.
 42. A can as defined in claim 41, wherein the can lid isformed with stiffening features selected from the group consisting ofraised ribs, depressed ribs, raised panel areas, depressed panel areasand coined areas.
 43. A can as defined in claim 38, wherein the can lidhas a diameter of about 2.25 inches.
 44. A can lid as defined in claim22, wherein the can lid member is substantially free of countersinking.45. A beverage package as defined in claim 23, wherein the can lid issubstantially free of countersinking.
 46. A can as defined in claim 45,wherein the can lid is formed with stiffening features selected from thegroup consisting of raised ribs, depressed ribs, raised panel areas,depressed panel areas and coined areas.
 47. A can as defined in claim 1,wherein said flange outer surface is oriented at an angle of slopebetween about 12.5° and about 40° to said plane.
 48. A can lid member asdefined in claim 21, wherein said flange outer surface is oriented at anangle of slope between about 12.5° and about 40° to said plane.
 49. Acan lid as defined in claim 22, wherein said flange outer surface isoriented at an angle of slope between about 12.5° and about 40° to saidplane.
 50. A beverage package as defined in claim 23, wherein saidflange outer surface is oriented at an angle of slope between about12.5° and about 40° to said plane.
 51. A method as defined in claim 24,wherein said flange outer surface is oriented at an angle of slopebetween about 12.5° and about 40° to said plane.
 52. A can as defined inclaim 1, wherein said flange outer surface is oriented at an angle ofslope between about 20° and about 35° to said plane.
 53. A can lidmember as defined in claim 21, wherein said flange outer surface isoriented at an angle of slope between about 20° and about 35° to saidplane.
 54. A can lid as defined in claim 22, wherein said flange outersurface is oriented at an angle of slope between about 20° and about 35°to said plane.
 55. A beverage package as defined in claim 23, whereinsaid flange outer surface is oriented at an angle of slope between about20° and about 35° to said plane.
 56. A method as defined in claim 24,wherein said flange outer surface is oriented at an angle of slopebetween about 20° and about 35° to said plane.
 57. A can as defined inclaim 1, wherein said flange outer surface is oriented at an angle ofslope between about 12.5° and about 30° to said plane.
 58. A can lidmember as defined in claim 21, wherein said flange outer surface isoriented at an angle of slope between about 12.5° and about 30° to saidplane.
 59. A can lid as defined in claim 22, wherein said flange outersurface is oriented at an angle of slope between about 12.5° and about30° to said plane.
 60. A beverage package as defined in claim 23,wherein said flange outer surface is oriented at an angle of slopebetween about 12.5° and about 30° to said plane.
 61. A method as definedin claim 24, wherein said flange outer surface is oriented at an angleof slope between about 12.5° and about 30° to said plane.